LeetCode minDepth of 2 bin tree

111. Minimum Depth of Binary Tree

题目：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 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) {          // Start typing your C/C++ solution below          // DO NOT write int main() function          return minRec(root);      }            int minRec( TreeNode * root) {          if(!root) return 0;                    if(root->left == NULL && root->right == NULL) return 1;        int leftDepth = minRec(root->left);        int rightDepth = minRec(root->right);        if(root->left == NULL)  return 1 + rightDepth;        else if(root->right == NULL) return 1 + leftDepth;        else return min(leftDepth,rightDepth) + 1;    }  };