Minimum Depth of Binary Tree（二叉树DFS）

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.

代码：

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
private:
int mindepth;
public:
    void tra(TreeNode* root,int depth){
        if(root==NULL) return;
        ++depth;
        if(!root->left&&!root->right&&depth!=&&depth<mindepth)//必须是叶节点才更新mindepth
        　　mindepth=depth;
        tra(root->left,depth);
        tra(root->right,depth);
    }
    int minDepth(TreeNode *root) {
        mindepth=;
        if(!root) return ;
        if(root->left==NULL&&root->right==NULL) return ;
        tra(root,);
        if(mindepth==){
            return ;
        }
        return mindepth;
    }
};