[LeetCode] Maximum Depth of Binary Tree (C++)

leetcode.com/problems/maximum-depth-of-binary-tree/

Maximum Depth of Binary Tree - LeetCode

역시나 리스트를 사용해 포인터의 개념이 필요했습니다. 트리의 DFS, BFS 탐색을 해보는 문제였습니다.

 

/**
 * 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) {}
 * };
 */
 
 /* DFS(Depth First Search) */
 
class Solution {
public:
    int maxDepth(TreeNode* root) {
        if(root == NULL) return 0;
        return max(maxDepth(root->left), maxDepth(root->right)) + 1;
    }
};

 

/**
 * 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) {}
 * };
 */
 
  /* BFS(Breadth First Search) */
 
class Solution {
public:
    int maxDepth(TreeNode* root) {
        if(root == NULL) return 0;
        int answer;
        queue<pair<TreeNode*, int > > q; // root, level을 저장
        q.push({ root, 1 });
        
        while(!q.empty()) {
            TreeNode* now = q.front().first;
            int cnt = q.front().second;
            answer = cnt;
            q.pop();

            if(now->left != NULL) q.push({ now->left, cnt + 1 });
            if(now->right != NULL) q.push({ now->right, cnt + 1 });
        }
        
        return answer;
    }
};