Leetcode题目：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.

题目解答：

这道题借助了之前做的层次遍历的题目的代码，增加了一个判断条件，如果可以确定当前节点是叶子节点，则返回其深度，也就是找到的最近的叶子节点的深度。

代码如下：

/**
 * 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) {
        int depth = 0;
        int curnum = 0;
        int childnum = 0;
        if(root == NULL)
        {
            return 0;
        }
        queue<TreeNode *> TreeQueue;
        TreeQueue.push(root);
        curnum = 1;
        while(curnum != 0)
        {
            vector<int> tmp;
            depth++;
            while(curnum != 0)
            {
                TreeNode *p = TreeQueue.front();
                tmp.push_back(p -> val);
                if((p -> left == NULL) && (p -> right == NULL))
                {
                    return depth;
                }
                if(p -> left != NULL)
                {
                    TreeQueue.push(p -> left);
                    childnum++;
                }
                if(p -> right != NULL)
                {
                    TreeQueue.push(p -> right);
                    childnum++;
                }
               
                TreeQueue.pop();
                curnum--;
            }
            curnum = childnum;
            childnum = 0;
        }
        return depth;
    }
};