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.

IDEA

求树的最小深度：

1.递归 先序遍历 （深度优先）

2.层序遍历（广度优先）

CODE

1.

class Solution {public:    int run(TreeNode *root) {        if(root==NULL)            return 0;        int left_depth=run(root->left);        int right_depth=run(root->right);        if(left_depth==0||right_depth==0)            return 1+left_depth+right_depth;        return 1+min(left_depth,right_depth);    }};2.
class Solution {public:    int run(TreeNode *root) {        if(root==NULL)            return 0;        int level=0;        queue<TreeNode*> que;        que.push(root);        while(!que.empty()){            int size=que.size();            level++;            while(size--){                TreeNode *p=que.front();                que.pop();                if(p->left==NULL&&p->right==NULL)                    return level;                if(p->left){                    que.push(p->left);                }	                if(p->right){                    que.push(p->right);                }               }        }        return level;    }};