LeetCode – Refresh – Minimum Depth of Binary Tree

 1 /**
 2  * Definition for binary tree
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     int minDepth(TreeNode *root) {
13         if (!root) return 0;
14         queue<TreeNode *> q;
15         q.push(root);
16         int current = 1, future = 0, level = 1;
17         while (!q.empty()) {
18             TreeNode *tmp = q.front();
19             q.pop(), current--;
20             if (!tmp->left && !tmp->right) return level;
21             if (tmp->left) {
22                 q.push(tmp->left);
23                 future++;
24             }
25             if (tmp->right) {
26                 q.push(tmp->right);
27                 future++;
28             }
29             if (!current) {
30                 current = future;
31                 future = 0;
32                 level++;
33             }
34         }
35     }
36 };