二叉树的最大深度与最小深度

给出一棵如下的二叉树:

1
/ \
2 3
…/ \
…4 5

/** * Definition of TreeNode: * class TreeNode { * public: *     int val; *     TreeNode *left, *right; *     TreeNode(int val) { *         this->val = val; *         this->left = this->right = NULL; *     } * } */class Solution {public:    /**     * @param root: The root of binary tree.     * @return: An integer     */    int maxDepth(TreeNode *root) {        // write your code here        if(root == NULL) return 0;        int leftMax = maxDepth(root ->left);        int rightMax = maxDepth(root ->right);        return max(leftMax,rightMax) + 1;    }};

最小深度

/** * Definition of TreeNode: * class TreeNode { * public: *     int val; *     TreeNode *left, *right; *     TreeNode(int val) { *         this->val = val; *         this->left = this->right = NULL; *     } * } */class Solution {public:    /**     * @param root: The root of binary tree.     * @return: An integer     */    int minDepth(TreeNode *root) {        // write your code here        if(root == NULL) return 0;        int res = helper(root);        return res;    }    int helper(TreeNode* root) {        if (root == NULL) return INT_MAX; //为空时，不能算深度        if(root ->left == NULL && root ->right == NULL) return 1; //叶结点深度为1        int left = helper(root ->left);        int right = helper(root ->right);        return min(left,right) + 1;    }};