leetcode 111：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.

class Solution {public:    int minDepth(TreeNode* root) {        int ret=1000000;        if(!root) return 0;        help(root,1,ret);        return ret;    }private:    void help(TreeNode* root,int depth,int& ret)    {        if(!root->left&&!root->right)            ret=min(depth,ret);        else if(root->left&&root->right)        {            help(root->left,depth+1,ret);            help(root->right,depth+1,ret);        }        else if(root->right&&!root->left)            help(root->right,depth+1,ret);        else            help(root->left,depth+1,ret);    }    int min(int a,int b)    {        return a<b?a:b;    }};

呵呵哒，老子很失落！

学习下大佬的代码：BFS

int minDepth(TreeNode* root) {    if (root == NULL) return 0;    queue<TreeNode*> Q;    Q.push(root);    int i = 0;    while (!Q.empty()) {        i++;        int k = Q.size();        for (int j=0; j<k; j++) {            TreeNode* rt = Q.front();            if (rt->left) Q.push(rt->left);            if (rt->right) Q.push(rt->right);            Q.pop();            if (rt->left==NULL && rt->right==NULL) return i;        }    }    return -1; //For the compiler thing. The code never runs here.}