添加 0226.翻转二叉树.md C语言版本

problems/0226.翻转二叉树.md

@@ -473,6 +473,51 @@ var invertTree = function(root) {
 };
 ```
 
+C:
+递归法
+```c
+struct TreeNode* invertTree(struct TreeNode* root){
+    if(!root)
+        return NULL;
+    //交换结点的左右孩子（中）
+    struct TreeNode* temp = root->right;
+    root->right = root->left;
+    root->left = temp;
+    左
+    invertTree(root->left);
+    //右
+    invertTree(root->right);
+    return root;
+}
+```
+迭代法：深度优先遍历
+```c
+struct TreeNode* invertTree(struct TreeNode* root){
+    if(!root)
+        return NULL;
+    //存储结点的栈
+    struct TreeNode** stack = (struct TreeNode**)malloc(sizeof(struct TreeNode*) * 100);
+    int stackTop = 0;
+    //将根节点入栈
+    stack[stackTop++] = root;
+    //若栈中还有元素（进行循环）
+    while(stackTop) {
+        //取出栈顶元素
+        struct TreeNode* temp = stack[--stackTop];
+        //交换结点的左右孩子
+        struct TreeNode* tempNode = temp->right;
+        temp->right = temp->left;
+        temp->left = tempNode;
+        //若当前结点有左右孩子，将其入栈
+        if(temp->right)
+            stack[stackTop++] = temp->right;
+        if(temp->left)
+            stack[stackTop++] = temp->left;
+    }
+    return root;
+}
+```
+
 -----------------------
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)