[leetcode]Binary Tree Right Side View

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<int> rightSideView(TreeNode *root) {
        vector<int> ans;
        if (root == nullptr) return ans;
        int cnt = 1;
        queue<TreeNode*> que;
        que.push(root);
        TreeNode* curr;
        while(!que.empty()) {
            int now_cnt = 0;
            for (int i = 0; i < cnt; i++) {
                curr = que.front(); que.pop();
                if (curr->left) {
                    que.push(curr->left);
                    now_cnt++;
                }
                if (curr->right) {
                    que.push(curr->right);
                    now_cnt++;
                }
            }
            ans.push_back(curr->val);
            cnt = now_cnt;
        }
        return ans;
    }
};