[面试真题] LeetCode：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.

分别考虑左右子树是否为空的情况并递归地进行计算。

Program Runtime: 60 milli secs

/**
 * Definition for binary tree
 * 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
        if(NULL == root){
            return 0;
        }
        if(root->left != NULL && root->right == NULL){
            return minDepth(root->left) + 1;
        }else if(root->left == NULL && root->right != NULL){
            return minDepth(root->right) + 1;
        }else if(root->left == NULL && root->right == NULL){
            return 1;
        }else{
            int left = minDepth(root->left);
            int right = minDepth(root->right);
            return 1 + (left < right ? left : right);
        }
    }
};