init

else/traverse.h

@@ -0,0 +1,138 @@
+//
+// Created by 李洋 on 2023/10/12.
+//
+
+#ifndef LEECODE_C_TRAVERSE_H
+#define LEECODE_C_TRAVERSE_H
+using namespace std;
+
+#include "structs/Tree.h"
+#include <queue>
+#include <stack>
+
+queue<TreeNode *> Q;
+
+// 递归写法 - int型
+// 先序遍历 preorder traversal
+void preorder_recursion_help(TreeNode *head) {
+    if (head != nullptr) {
+        Q.push(head);
+        preorder_recursion_help(head->left);
+        preorder_recursion_help(head->right);
+    }
+}
+
+queue<TreeNode *> preorder_recursion(TreeNode *head) {
+    preorder_recursion_help(head);
+    return Q;
+};
+
+// 中序遍历 inorder traversal
+void inorder_recursion_help(TreeNode *head) {
+    if (head != nullptr) {
+        inorder_recursion_help(head->left);
+        Q.push(head);
+        inorder_recursion_help(head->right);
+    }
+}
+
+queue<TreeNode *> inorder_recursion(TreeNode *head) {
+    inorder_recursion_help(head);
+    return Q;
+};
+
+// 后序遍历 postorder traversal
+void postorder_recursion_help(TreeNode *head) {
+    if (head != nullptr) {
+        postorder_recursion_help(head->left);
+        postorder_recursion_help(head->right);
+        Q.push(head);
+    }
+}
+
+queue<TreeNode *> postorder_recursion(TreeNode *head) {
+    postorder_recursion_help(head);
+    return Q;
+};
+
+// 非递归写法
+// 先序遍历 preorder traversal
+queue<TreeNode *> preorder(TreeNode *head) {
+    if (!head) {
+        return Q;
+    }
+
+    auto temp = head;
+
+    stack < TreeNode * > S;
+
+    S.push(temp);
+
+    TreeNode *t;
+
+    while (!S.empty()) {
+        t = S.top();
+        S.pop();
+        Q.push(t);
+        if (t->right)
+            S.push(t->right);
+        if (t->left)
+            S.push(t->left);
+    }
+    return Q;
+}
+
+// 中序遍历 inorder traversal
+queue<TreeNode *> inorder(TreeNode *head) {
+    auto temp = head;
+    stack < TreeNode * > S;
+
+    while (temp != nullptr || !S.empty()) {
+        if (temp) {
+            S.push(temp);
+            temp = temp->left;
+            continue;
+        }
+        temp = S.top();
+        Q.push(temp);
+        S.pop();
+        temp = temp->right;
+    }
+    return Q;
+}
+
+// 后序遍历 postorder traversal
+queue<TreeNode *> postorder(TreeNode *head) {
+    auto temp = head;
+    stack <pair<TreeNode *, bool>> S;
+
+    while (temp != nullptr || !S.empty()) {
+        if (temp) {
+            S.emplace(temp, false);
+            temp = temp->left;
+            continue;
+        }
+        temp = S.top().first;
+
+        if (temp->right == nullptr || S.top().second) {
+            Q.push(temp);
+            S.pop();
+            temp = nullptr;
+            continue;
+        }
+        S.top().second = true;
+        temp = temp->right;
+    }
+    return Q;
+}
+
+void test1() {
+    auto TreeNode = createRandomTree(10);
+    auto Q = postorder(TreeNode);
+    while (!Q.empty()) {
+        cout << Q.front()->val << " ";
+        Q.pop();
+    }
+}
+
+#endif //LEECODE_C_TRAVERSE_H