LeetCode：Minimum Depth of Binary Tree

class Solution {
public:
int minDepth(TreeNode *root) {
// Start typing your C/C++ solution below
// DO NOT write int main() function

if(root == NULL)
return 0;
int level = 1;
vector<TreeNode*>tree;
tree.push_back(root);
int begin = 0;
int end = 1;
while(begin<end)
{
TreeNode* node = tree[begin];
if(node->right==NULL&&node->left==NULL)
return level;
if(node->right)
tree.push_back(node->right);
if(node->left)
tree.push_back(node->left);
if(begin == end-1)
{
end = tree.size();
level++;
}
begin++;
}

}
};