[Update]

1. Update topic names of Pyhon file.
2. Replace the binary tree printer with a more clear one.
3. Update README.

.gitignore

@@ -0,0 +1,3 @@
+__pycache__
+.vscode
+.DS_Store

README.md

@@ -10,7 +10,7 @@ LeetBook《图解算法数据结构》面向算法初学者、互联网求职者
 
 ### :green_book: 剑指 Offer 图文题解
 
-- 图文详解 75 道题目，覆盖主要算法知识点，非常适合作为算法学习的**第一份题库**。
+- 图文详解 75 道题目，覆盖主要算法知识点，非常适合作为算法学习的 **第一份题库** 。
 - 题库活跃于各大互联网公司招聘中，可使笔面试准备事半功倍。
 - 致力于行文深入浅出、图文搭配，提供简洁的 **Python3, Java, C++** 解题代码。
 - 笔者整理了 **30 天刷题计划**、**题目分类**，让刷题有迹可循。
@@ -35,8 +35,8 @@ LeetBook《图解算法数据结构》面向算法初学者、互联网求职者
 
 > 建议对数据结构不熟悉的同学，先看这篇熟悉用法。
 
-- 常用数据结构的**分类**和**基本特点**；
-- 在算法解题中，数据结构的**常用操作**；
+- 常用数据结构的**分类**和**基本特点**。
+- 在算法解题中，数据结构的**常用操作**。
 - 在 Python3 , Java , C++ 语言中，各数据结构的**初始化与构建方法**。
 
 ### 「[算法复杂度](https://leetcode-cn.com/leetbook/read/illustration-of-algorithm/r84gmi/)」

cpp/include/PrintUtil.hpp

@@ -12,130 +12,186 @@
 #include "ListNode.hpp"
 #include "TreeNode.hpp"
 
-/**
- * @brief Find an element in a vector
- * 
- * @tparam T 
- * @param vec 
- * @param ele 
- * @return int 
- */
-template <typename T>
-int vecFind(const vector<T>& vec, T ele) {
-    int j = INT_MAX;
-    for (int i = 0; i < vec.size(); i++) {
-        if (vec[i] == ele) {
-            j = i;
+class PrintUtil {
+    public:
+        /**
+         * @brief Find an element in a vector
+         * 
+         * @tparam T 
+         * @param vec 
+         * @param ele 
+         * @return int 
+         */
+        template <typename T>
+        static int vecFind(const vector<T>& vec, T ele) {
+            int j = INT_MAX;
+            for (int i = 0; i < vec.size(); i++) {
+                if (vec[i] == ele) {
+                    j = i;
+                }
+            }
+            return j;
         }
-    }
-    return j;
-}
 
-/**
- * @brief Concatenate a vector with a delim
- * 
- * @tparam T 
- * @param delim 
- * @param vec 
- * @return string 
- */
-template <typename T>
-string join(const string& delim, const T& vec) {
-    ostringstream s;
-    for (const auto& i : vec) {
-        if (&i != &vec[0]) {
-            s << delim;
+        /**
+         * @brief Concatenate a vector with a delim
+         * 
+         * @tparam T 
+         * @param delim 
+         * @param vec 
+         * @return string 
+         */
+        template <typename T>
+        static string strJoin(const string& delim, const T& vec) {
+            ostringstream s;
+            for (const auto& i : vec) {
+                if (&i != &vec[0]) {
+                    s << delim;
+                }
+                s << i;
+            }
+            return s.str();
         }
-        s << i;
-    }
-    return s.str();
-}
 
-/**
- * @brief Repeat a string for n times
- * 
- * @param str 
- * @param n 
- * @return string 
- */
-string repeat(string str, int n) {
-    ostringstream os;
-    for(int i = 0; i < n; i++)
-        os << str;
-    return os.str();
-}
+        /**
+         * @brief Repeat a string for n times
+         * 
+         * @param str 
+         * @param n 
+         * @return string 
+         */
+        static string strRepeat(string str, int n) {
+            ostringstream os;
+            for(int i = 0; i < n; i++)
+                os << str;
+            return os.str();
+        }
 
-/**
- * @brief Get the Vector String object
- * 
- * @tparam T 
- * @param list 
- * @return string 
- */
-template <typename T>
-string getVectorString(vector<T> &list) {
-    return "[" + join(", ", list) + "]";
-}
+        /**
+         * @brief Get the Vector String object
+         * 
+         * @tparam T 
+         * @param list 
+         * @return string 
+         */
+        template <typename T>
+        static string getVectorString(vector<T> &list) {
+            return "[" + strJoin(", ", list) + "]";
+        }
 
-/**
- * @brief Print a vector
- * 
- * @tparam T 
- * @param list 
- */
-template <typename T>
-void printVector(vector<T> &list) {
-    cout << getVectorString(list) << '\n';
-}
+        /**
+         * @brief Print a vector
+         * 
+         * @tparam T 
+         * @param list 
+         */
+        template <typename T>
+        static void printVector(vector<T> &list) {
+            cout << getVectorString(list) << '\n';
+        }
 
-/**
- * @brief Print a vector matrix
- * 
- * @tparam T 
- * @param matrix 
- */
-template <typename T>
-void printVectorMatrix(vector<vector<T>> &matrix) {
-    cout << "[" << '\n';
-    for (vector<T> &list : matrix)
-        cout << "  " + getVectorString(list) + "," << '\n';
-    cout << "]" << '\n';
-}
+        /**
+         * @brief Print a vector matrix
+         * 
+         * @tparam T 
+         * @param matrix 
+         */
+        template <typename T>
+        static void printVectorMatrix(vector<vector<T>> &matrix) {
+            cout << "[" << '\n';
+            for (vector<T> &list : matrix)
+                cout << "  " + getVectorString(list) + "," << '\n';
+            cout << "]" << '\n';
+        }
 
-/**
- * @brief Print a linked list
- * 
- * @param head 
- */
-void printLinkedList(ListNode *head) {
-    vector<int> list;
-    while (head != nullptr) {
-        list.push_back(head->val);
-        head = head->next;
-    }
-    
-    cout << join(" -> ", list) << '\n';
-}
+        /**
+         * @brief Print a linked list
+         * 
+         * @param head 
+         */
+        static void printLinkedList(ListNode *head) {
+            vector<int> list;
+            while (head != nullptr) {
+                list.push_back(head->val);
+                head = head->next;
+            }
+            
+            cout << strJoin(" -> ", list) << '\n';
+        }
 
-/**
- * @brief Print helper for binary tree
- * 
- * @param root 
- * @param level 
- */
-void printTreeHelper(TreeNode *root, int level) {
-    if (root == nullptr)
-        return;
-    printTreeHelper(root->right, level + 1); 
-    cout << repeat(" ", 4 * level) + "->" << root->val << '\n';
-    printTreeHelper(root->left, level + 1);
-}
+        /**
+         * @brief This tree printer is borrowed from TECHIE DELIGHT
+         *        https://www.techiedelight.com/c-program-print-binary-tree/
+         */
+        struct Trunk {
+            Trunk *prev;
+            string str;
+            Trunk(Trunk *prev, string str) {
+                this->prev = prev;
+                this->str = str;
+            }
+        };
+        
+        /**
+         * @brief Helper function to print branches of the binary tree
+         * 
+         * @param p 
+         */
+        static void showTrunks(Trunk *p) {
+            if (p == nullptr) {
+                return;
+            }
+        
+            showTrunks(p->prev);
+            cout << p->str;
+        }
 
-/**
- * @brief Print a binary tree (90º counter-clockwise rotated)
- * 
- * @param root 
- */
-void printTree(TreeNode *root) {
-    printTreeHelper(root, 0);
-}
+        /**
+         * @brief The interface of the tree printer
+         * 
+         * @param root 
+         */
+        static void printTree(TreeNode *root) {
+            printTree(root, nullptr, false);
+        }
+
+        /**
+         * @brief Print a binary tree
+         * 
+         * @param root 
+         * @param prev 
+         * @param isLeft 
+         */
+        static void printTree(TreeNode *root, Trunk *prev, bool isLeft) {
+            if (root == nullptr) {
+                return;
+            }
+        
+            string prev_str = "    ";
+            Trunk *trunk = new Trunk(prev, prev_str);
+        
+            printTree(root->right, trunk, true);
+        
+            if (!prev) {
+                trunk->str = "———";
+            }
+            else if (isLeft) {
+                trunk->str = "/———";
+                prev_str = "   |";
+            }
+            else {
+                trunk->str = "\\———";
+                prev->str = prev_str;
+            }
+        
+            showTrunks(trunk);
+            cout << " " << root->val << endl;
+        
+            if (prev) {
+                prev->str = prev_str;
+            }
+            trunk->str = "   |";
+        
+            printTree(root->left, trunk, false);
+        }
+};

cpp/sfo_06_print_a_linked_list_in_reverse_order_s1/sfo_06_print_a_linked_list_in_reverse_order_s1.cpp

@@ -28,7 +28,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<int> res = slt->reversePrint(head);
-    printVector(res);
+    PrintUtil::printVector(res);
     
     return 0;
 }

cpp/sfo_06_print_a_linked_list_in_reverse_order_s2/sfo_06_print_a_linked_list_in_reverse_order_s2.cpp

@@ -30,7 +30,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<int> res = slt->reversePrint(head);
-    printVector(res);
+    PrintUtil::printVector(res);
     
     return 0;
 }

cpp/sfo_07_reconstruct_binary_tree_s1/sfo_07_reconstruct_binary_tree_s1.cpp

@@ -35,7 +35,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     TreeNode* res = slt->buildTree(preorder, inorder);
-    printTree(res);
+    PrintUtil::printTree(res);
     
     return 0;
 }

cpp/sfo_09_implement_a_queue_using_two_stacks_s1/sfo_09_implement_a_queue_using_two_stacks_s1.cpp

@@ -41,7 +41,7 @@ int main() {
     cQueue->appendTail(2);
     res.push_back(cQueue->deleteHead());
     res.push_back(cQueue->deleteHead());
-    printVector(res);
+    PrintUtil::printVector(res);
 
     return 0;
 }

cpp/sfo_18_delete_a_node_from_a_linked_list_s1/sfo_18_delete_a_node_from_a_linked_list_s1.cpp

@@ -28,7 +28,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     ListNode* res = slt->deleteNode(head, val);
-    printLinkedList(res);
+    PrintUtil::printLinkedList(res);
     
     return 0;
 }

cpp/sfo_21_adjust_the_order_of_numbers_in_an_array_s1/sfo_21_adjust_the_order_of_numbers_in_an_array_s1.cpp

@@ -27,7 +27,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<int> res = slt->exchange(nums);
-    printVector(res);
+    PrintUtil::printVector(res);
     
     return 0;
 }

cpp/sfo_22_the_kth_node_from_the_end_of_a_linked_list_s1/sfo_22_the_kth_node_from_the_end_of_a_linked_list_s1.cpp

@@ -28,7 +28,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     ListNode* res = slt->getKthFromEnd(head, k);
-    printLinkedList(res);
+    PrintUtil::printLinkedList(res);
     
     return 0;
 }

cpp/sfo_22_the_kth_node_from_the_end_of_a_linked_list_s2/sfo_22_the_kth_node_from_the_end_of_a_linked_list_s2.cpp

@@ -30,7 +30,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     ListNode* res = slt->getKthFromEnd(head, k);
-    printLinkedList(res);
+    PrintUtil::printLinkedList(res);
     
     return 0;
 }

cpp/sfo_24_reverse_a_linked_list_s1/sfo_24_reverse_a_linked_list_s1.cpp

@@ -27,7 +27,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     ListNode* res = slt->reverseList(head);
-    printLinkedList(res);
+    PrintUtil::printLinkedList(res);
     
     return 0;
 }

cpp/sfo_24_reverse_a_linked_list_s2/sfo_24_reverse_a_linked_list_s2.cpp

@@ -27,7 +27,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     ListNode* res = slt->reverseList(head);
-    printLinkedList(res);
+    PrintUtil::printLinkedList(res);
     
     return 0;
 }

cpp/sfo_25_combine_two_sorted_linked_lists_s1/sfo_25_combine_two_sorted_linked_lists_s1.cpp

@@ -35,7 +35,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     ListNode* res = slt->mergeTwoLists(l1, l2);
-    printLinkedList(res);
+    PrintUtil::printLinkedList(res);
     
     return 0;
 }

cpp/sfo_27_mirror_of_a_binary_tree_s1/sfo_27_mirror_of_a_binary_tree_s1.cpp

@@ -24,7 +24,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     TreeNode* res = slt->mirrorTree(root);
-    printTree(res);
+    PrintUtil::printTree(res);
     
     return 0;
 }

cpp/sfo_27_mirror_of_a_binary_tree_s2/sfo_27_mirror_of_a_binary_tree_s2.cpp

@@ -33,7 +33,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     TreeNode* res = slt->mirrorTree(root);
-    printTree(res);
+    PrintUtil::printTree(res);
     
     return 0;
 }

cpp/sfo_29_print_a_given_matrix_in_spiral_form_s1/sfo_29_print_a_given_matrix_in_spiral_form_s1.cpp

@@ -38,7 +38,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<int> res = slt->spiralOrder(matrix);
-    printVector(res);
+    PrintUtil::printVector(res);
     
     return 0;
 }

cpp/sfo_30_min_stack_s1/sfo_30_min_stack_s1.cpp

@@ -40,7 +40,7 @@ int main() {
     minStack->pop();
     res.push_back(minStack->top());
     res.push_back(minStack->min());
-    printVector(res);
+    PrintUtil::printVector(res);
 
     return 0;
 }

cpp/sfo_32i_print_a_binary_tree_topbottom_i_s1/sfo_32i_print_a_binary_tree_topbottom_i_s1.cpp

@@ -31,7 +31,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<int> res = slt->levelOrder(root);
-    printVector(res);
+    PrintUtil::printVector(res);
     
     return 0;
 }

cpp/sfo_32ii_print_a_binary_tree_topbottom_ii_s1/sfo_32ii_print_a_binary_tree_topbottom_ii_s1.cpp

@@ -35,7 +35,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<vector<int>> res = slt->levelOrder(root);
-    printVectorMatrix(res);
+    PrintUtil::printVectorMatrix(res);
     
     return 0;
 }

cpp/sfo_32iii_print_a_binary_tree_topbottom_iii_s1/sfo_32iii_print_a_binary_tree_topbottom_iii_s1.cpp

@@ -50,7 +50,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<vector<int>> res = slt->levelOrder(root);
-    printVectorMatrix(res);
+    PrintUtil::printVectorMatrix(res);
     
     return 0;
 }

cpp/sfo_32iii_print_a_binary_tree_topbottom_iii_s2/sfo_32iii_print_a_binary_tree_topbottom_iii_s2.cpp

@@ -35,7 +35,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<vector<int>> res = slt->levelOrder(root);
-    printVectorMatrix(res);
+    PrintUtil::printVectorMatrix(res);
     
     return 0;
 }

cpp/sfo_34_all_xsum_paths_in_a_binary_tree_s1/sfo_34_all_xsum_paths_in_a_binary_tree_s1.cpp

@@ -35,7 +35,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<vector<int>> res = slt->pathSum(root, sum);
-    printVectorMatrix(res);
+    PrintUtil::printVectorMatrix(res);
     
     return 0;
 }

cpp/sfo_35_clone_a_linked_list_with_next_and_random_pointer_s1/sfo_35_clone_a_linked_list_with_next_and_random_pointer_s1.cpp

@@ -74,9 +74,9 @@ int main() {
     for (int i = 0; i < nodeListNew.size(); i++) {
         Node* node = nodeListNew[i];
         printArr[i][0] = node->val;
-        printArr[i][1] = vecFind(nodeListNew, node->random);
+        printArr[i][1] = PrintUtil::vecFind(nodeListNew, node->random);
     }
-    printVectorMatrix(printArr);
+    PrintUtil::printVectorMatrix(printArr);
     
     return 0;
 }

cpp/sfo_35_clone_a_linked_list_with_next_and_random_pointer_s2/sfo_35_clone_a_linked_list_with_next_and_random_pointer_s2.cpp

@@ -84,9 +84,9 @@ int main() {
     for (int i = 0; i < nodeListNew.size(); i++) {
         Node* node = nodeListNew[i];
         printArr[i][0] = node->val;
-        printArr[i][1] = vecFind(nodeListNew, node->random);
+        printArr[i][1] = PrintUtil::vecFind(nodeListNew, node->random);
     }
-    printVectorMatrix(printArr);
+    PrintUtil::printVectorMatrix(printArr);
     
     return 0;
 }

cpp/sfo_36_binary_search_tree_and_doubly_linked_list_s1/sfo_36_binary_search_tree_and_doubly_linked_list_s1.cpp

@@ -63,7 +63,7 @@ int main() {
         nodesVal.push_back(res->val);
         res = res->right;
     }
-    cout << join(" <-> ", nodesVal) << endl;
+    cout << PrintUtil::strJoin(" <-> ", nodesVal) << endl;
     
     return 0;
 }

cpp/sfo_37_serialize_and_deserialize_a_binary_tree_s1/sfo_37_serialize_and_deserialize_a_binary_tree_s1.cpp

@@ -75,6 +75,6 @@ int main() {
     Codec* codec = new Codec();
     TreeNode* root = codec->deserialize(data);
     string res = codec->serialize(root);
-    printTree(root);
+    PrintUtil::printTree(root);
     cout << res << endl;
 }

cpp/sfo_38_all_permutations_of_a_string_s1/sfo_38_all_permutations_of_a_string_s1.cpp

@@ -37,7 +37,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<string> res = slt->permutation(s);
-    printVector(res);
+    PrintUtil::printVector(res);
     
     return 0;
 }

cpp/sfo_40_the_smallest_k_numbers_s1/sfo_40_the_smallest_k_numbers_s1.cpp

@@ -40,7 +40,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<int> res = slt->getLeastNumbers(arr, k);
-    printVector(res);
+    PrintUtil::printVector(res);
     
     return 0;
 }

cpp/sfo_40_the_smallest_k_numbers_s2/sfo_40_the_smallest_k_numbers_s2.cpp

@@ -37,7 +37,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<int> res = slt->getLeastNumbers(arr, k);
-    printVector(res);
+    PrintUtil::printVector(res);
     
     return 0;
 }

cpp/sfo_41_find_median_from_data_stream_s1/sfo_41_find_median_from_data_stream_s1.cpp

@@ -37,7 +37,7 @@ int main() {
     res.push_back(medianFinder->findMedian());
     medianFinder->addNum(3);
     res.push_back(medianFinder->findMedian());
-    printVector(res);
+    PrintUtil::printVector(res);
 
     return 0;
 }

cpp/sfo_56i_single_number_i_s1/sfo_56i_single_number_i_s1.cpp

@@ -29,7 +29,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<int> res = slt->singleNumbers(nums);
-    printVector(res);
+    PrintUtil::printVector(res);
     
     return 0;
 }

cpp/sfo_57_two_numbers_with_sum_s_s1/sfo_57_two_numbers_with_sum_s_s1.cpp

@@ -28,7 +28,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<int> res = slt->twoSum(nums, target);
-    printVector(res);
+    PrintUtil::printVector(res);
     
     return 0;
 }

cpp/sfo_57ii_consecutive_numbers_with_sum_s_s1/sfo_57ii_consecutive_numbers_with_sum_s_s1.cpp

@@ -33,7 +33,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<vector<int>> res = slt->findContinuousSequence(target);
-    printVectorMatrix(res);
+    PrintUtil::printVectorMatrix(res);
     
     return 0;
 }

cpp/sfo_57ii_consecutive_numbers_with_sum_s_s2/sfo_57ii_consecutive_numbers_with_sum_s_s2.cpp

@@ -37,7 +37,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<vector<int>> res = slt->findContinuousSequence(target);
-    printVectorMatrix(res);
+    PrintUtil::printVectorMatrix(res);
     
     return 0;
 }

cpp/sfo_59ii_max_queue_s1/sfo_59ii_max_queue_s1.cpp

@@ -40,7 +40,7 @@ int main() {
     res.push_back(maxQueue->max_value());
     res.push_back(maxQueue->pop_front());
     res.push_back(maxQueue->max_value());
-    printVector(res);
+    PrintUtil::printVector(res);
 
     return 0;
 }

cpp/sfo_60_probabilities_for_rolling_n_dices_s1/sfo_60_probabilities_for_rolling_n_dices_s1.cpp

@@ -30,7 +30,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<double> res = slt->dicesProbability(n);
-    printVector(res);
+    PrintUtil::printVector(res);
     
     return 0;
 }

cpp/sfo_66_a_product_array_puzzle_s1/sfo_66_a_product_array_puzzle_s1.cpp

@@ -32,7 +32,7 @@ int main() {
     // ====== Driver Code ======
     Solution* slt = new Solution();
     vector<int> res = slt->constructArr(a);
-    printVector(res);
+    PrintUtil::printVector(res);
     
     return 0;
 }

java/include/PrintUtil.java

@@ -2,6 +2,16 @@ package include;
 
 import java.util.*;
 
+class Trunk {
+    Trunk prev;
+    String str;
+
+    Trunk(Trunk prev, String str) {
+        this.prev = prev;
+        this.str = str;
+    }
+};
+
 public class PrintUtil {
     /**
      * Print a linked list
@@ -17,23 +27,58 @@ public class PrintUtil {
     }
 
     /**
-     * Print a binary tree (90º counter-clockwise rotated)
+     * The interface of the tree printer
+     * This tree printer is borrowed from TECHIE DELIGHT
+     * https://www.techiedelight.com/c-program-print-binary-tree/
      * @param root
      */
     public static void printTree(TreeNode root) {
-        printTreeHelper(root, 0);
+        printTree(root, null, false);
     }
 
     /**
-     * Print helper for binary tree
+     * Print a binary tree
      * @param root
-     * @param level
+     * @param prev
+     * @param isLeft
      */
-    private static void printTreeHelper(TreeNode root, int level) {
-        if (root == null)
+    public static void printTree(TreeNode root, Trunk prev, boolean isLeft) {
+        if (root == null) {
             return;
-        printTreeHelper(root.right, level + 1);
-        System.out.println(" ".repeat(4 * level) + "->" + root.val);
-        printTreeHelper(root.left, level + 1);
+        }
+
+        String prev_str = "    ";
+        Trunk trunk = new Trunk(prev, prev_str);
+
+        printTree(root.right, trunk, true);
+
+        if (prev == null) {
+            trunk.str = "———";
+        } else if (isLeft) {
+            trunk.str = "/———";
+            prev_str = "   |";
+        } else {
+            trunk.str = "\\———";
+            prev.str = prev_str;
+        }
+
+        showTrunks(trunk);
+        System.out.println(" " + root.val);
+
+        if (prev != null) {
+            prev.str = prev_str;
+        }
+        trunk.str = "   |";
+
+        printTree(root.left, trunk, false);
+    }
+
+    public static void showTrunks(Trunk p) {
+        if (p == null) {
+            return;
+        }
+
+        showTrunks(p.prev);
+        System.out.print(p.str);
     }
 }

python/include/print_util.py

@@ -28,16 +28,46 @@ def print_linked_list(head):
     arr = linked_list_to_list(head)
     print(' -> '.join([str(a) for a in arr]))
 
-def print_tree(root):
-    """Print a binary tree (90º counter-clockwise rotated)
 
+class Trunk:
+    def __init__(self, prev=None, str=None):
+        self.prev = prev
+        self.str = str
+ 
+def showTrunks(p):
+    if p is None:
+        return
+    showTrunks(p.prev)
+    print(p.str, end='')
+ 
+def print_tree(root, prev=None, isLeft=False):
+    """Print a binary tree
+       This tree printer is borrowed from TECHIE DELIGHT
+       https://www.techiedelight.com/c-program-print-binary-tree/
     Args:
         root ([type]): [description]
-    """    
-    def helper(root, level):
-        if not root:
-            return
-        helper(root.right, level + 1)
-        print(' ' * 4 * level + '->', root.val)
-        helper(root.left, level + 1)
-    helper(root, 0)
+        prev ([type], optional): [description]. Defaults to None.
+        isLeft (bool, optional): [description]. Defaults to False.
+    """
+    if root is None:
+        return
+ 
+    prev_str = '    '
+    trunk = Trunk(prev, prev_str)
+    print_tree(root.right, trunk, True)
+ 
+    if prev is None:
+        trunk.str = '———'
+    elif isLeft:
+        trunk.str = '/———'
+        prev_str = '   |'
+    else:
+        trunk.str = '\———'
+        prev.str = prev_str
+ 
+    showTrunks(trunk)
+    print(' ' + str(root.val))
+    if prev:
+        prev.str = prev_str
+    trunk.str = '   |'
+    print_tree(root.left, trunk, False)