leetcode111---Minimum Depth of Binary Tree

问题描述：

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.

方法一：DFS

/**
* 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) {
if(!root) return 0;
int left = minDepth(root->left);
int right = minDepth(root->right);
return (left==0 || right==0)?(left+right+1):min(left, right)+1;
}
};

方法二：BFS

class Solution {
public:
// BFS
int minDepth(TreeNode *root) {
int res = 0;
queue<TreeNode *> myQueue;
if (root)
myQueue.push(root);
while (!myQueue.empty()) {
int l = myQueue.size();
res++;
for (int i = 0; i < l; i++) {
TreeNode *tmp = myQueue.front();
if (!(tmp->left) && !(tmp->right))
return res;
if (tmp->left)
myQueue.push(tmp->left);
if (tmp->right)
myQueue.push(tmp->right);
myQueue.pop();
}
}
return res;
}
};