添加 0222.完全二叉树的结点个数.md

problems/0222.完全二叉树的节点个数.md

@@ -495,6 +495,35 @@ int countNodes(struct TreeNode* root){
 }
 ```
 
+满二叉树
+```c
+int countNodes(struct TreeNode* root){
+    if(!root)
+        return 0;
+    int leftHeight = 0;
+    int rightHeight = 0;
+    struct TreeNode* rightNode = root->right;
+    struct TreeNode* leftNode = root->left;
+    //求出左子树深度
+    while(leftNode) {
+        leftNode = leftNode->left;
+        leftHeight++;
+    }
+
+    //求出右子树深度
+    while(rightNode) {
+        rightNode = rightNode->right;
+        rightHeight++;
+    }
+    //若左右子树深度相同，为满二叉树。结点个数为2^height-1
+    if(rightHeight == leftHeight) {
+        return (2 << leftHeight) - 1;
+    }
+    //否则返回左右子树的结点个数+1
+    return countNodes(root->right) + countNodes(root->left) + 1;
+}
+```
+
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 * 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)