102. Binary Tree Level Order Traversal

https://leetcode.com/problems/binary-tree-level-order-traversal/

Binary Tree Level Order Traversal - LeetCode

 

이진 트리가 주어졌을 때, 레벨별로 Node의 값을 이중 벡터에 담아 리턴하면 되는 문제다.

1레벨 값: ~~~~

2레벨 값: ~~~~

3레벨 값: ~~~~

4레벨 값: ~~~~

root부터 leaf node까지 내려가며 벡터에 추가하면 끝

 

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    void levelOrder(TreeNode* node, int level) {
        if (node == nullptr) {
            return;
        }

        if (v.empty() || v.size() < level) {
            v.push_back(vector<int>(1, node->val));
        }
        else {
            v[level -1].push_back(node->val);
        }

        if (node->left) {
            levelOrder(node->left, level + 1);
        }
        if (node->right) {
            levelOrder(node->right, level + 1);
        }
    }
    vector<vector<int>> levelOrder(TreeNode* root) {
        levelOrder(root, 1);
        return v;
    }
private:
    vector<vector<int>> v;
};