Minimum Depth of Binary Tree

Given a binary tree, find its minimum depth.

The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

class Solution {
public:
    int minDepth(TreeNode *root) {
        if(!root)//空树
            return 0;
        else if(!root->left && !root->right)//只有根结点
            return 1;
        else if(root->left && !root->right)//只有左子树
            return minDepth(root->left) + 1;
        else if(!root->left && root->right)//只有右子树
            return minDepth(root->right) + 1;
        return min(minDepth(root->left), minDepth(root->right)) + 1;
    }
    
    int min(int a, int b)
    {
        return a>b?b:a;
    }
};

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

class Solution {
public:
    int maxDepth(TreeNode *root) {
        if(!root)//空树
            return 0;
        else if(!root->left && !root->right)//只有根结点
            return 1;
        else if(root->left && !root->right)//只有左子树
            return maxDepth(root->left) + 1;
        else if(!root->left && root->right)//只有右子树
            return maxDepth(root->right) + 1;
        return max(maxDepth(root->left), maxDepth(root->right)) + 1;
    }
    
    int max(int a, int b)
    {
        return a>b?a:b;
    }
};