Minimum Depth of Binary Tree--LeetCode

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.

思路：这里递归就需要注意一些东西了，对于非递归来说，只要发现有一个节点没有左子树同时也没有右子树，那么这个就是节点所在层次就是目标

int MinDepth(BinTree* root)
{
    if(root == NULL)
        return 0;
    if(root->left == NULL)
        return MinDepth(root->right)+1;
    if(root->right == NULL)
        return MinDepth(root->left)+1;
    return min(MinDepth(root->left),MinDepth(root->right))+1;
}
int MinDepth_second(BinTree* root)
{
    if(root == NULL)
        return 0;
    BinTree* node;
    deque<BinTree*> de;
    int num;
    int curnum=0;
    int level=0;
    de.push_back(root);
    num=1;
    while(!de.empty()) 
    {
        node = de.front();
        de.pop_front();
        num--;
        if(node->left==NULL && node->right == NULL)
            return level+1;
        if(node->left != NULL)
        {
            de.push_back(node->left);
            curnum++;
        }
        if(node->right !=NULL)
        {
            de.push_back(node->right);
            curnum++;
        }    
        if(num == 0)
        {
            num = curnum;
            curnum=0;
            level++;
        }
    }
    return level;
}