用c语言写一个求二叉树深度的算法

以下是用 C 语言编写求二叉树深度的算法：

#include <stdio.h>
#include <stdlib.h>

struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
};

int maxDepth(struct TreeNode* root) {
    if (root == NULL) {
        return 0;
    }
    int leftDepth = maxDepth(root->left);
    int rightDepth = maxDepth(root->right);
    return leftDepth > rightDepth ? leftDepth + 1 : rightDepth + 1;
}

int main() {
    // 构造一棵二叉树
    struct TreeNode* root = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->val = 1;
    root->left = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->left->val = 2;
    root->left->left = NULL;
    root->left->right = NULL;
    root->right = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->right->val = 3;
    root->right->left = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->right->left->val = 4;
    root->right->left->left = NULL;
    root->right->left->right = NULL;
    root->right->right = NULL;

    // 计算二叉树深度
    int depth = maxDepth(root);
    printf("Depth of the binary tree is %d\n", depth);

    // 释放内存
    free(root->left);
    free(root->right->left);
    free(root->right);
    free(root);

    return 0;
}

这个算法的时间复杂度是 O(n)，其中 n 是二叉树中节点的个数。