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.

方法： 前序遍历，注意代码简洁度。
自己写的

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int minDepth(TreeNode* root) {
        if(!root)
            return 0;
        if(!root->left && !root->right)
            return 1;
        int left = minDepth(root->left);
        int right = minDepth(root->right);
        int min_depth = min(left,right);
        if(left == 0)
            min_depth = right;
        if(right == 0)
            min_depth = left;
        return 1 + min_depth ;

    }
};

简洁的代码：

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int minDepth(TreeNode* root) {
        if(!root)
            return 0;
        if(!root->left)
            return 1 + minDepth(root->right);
        if(!root->right)
            return 1 + minDepth(root->left);


        return 1 + min(minDepth(root->left),minDepth(root->right)) ;

    }
};