【Leetcode長征系列】Minimum Depth of Binary Tree

原題：

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.

思路：

遞歸實現深度優先，開闢全局變量記錄最小depth值！

代碼如下：

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
    int min = INT_MAX;
public:
    int minDepth(TreeNode *root) {
        int depth = 0;
        if(root==NULL) return 0;
        
        dfs(root,depth);        
        return min;
    }
    
    int dfs(TreeNode *root, int depth){
        if(root==NULL) return 0;
        
        depth++;
        if(root->left==NULL && root->right==NULL) return min = depth>min?min:depth;
        
        dfs(root->left, depth);
        dfs(root->right,depth);
    }
};

這麼多天…終於遇到一道簡單點的題了……………