437. Path Sum III

문제

https://leetcode.com/problems/path-sum-iii/description/

풀이

class Solution {
    int answer = 0;
    public int pathSum(TreeNode root, int targetSum) {
        if(root == null) {
            return 0;
        }
        DFS(root, 0, targetSum);
        pathSum(root.left, targetSum);
        pathSum(root.right, targetSum);
        return answer;
    }

    public void DFS(TreeNode node, long sum, int targetSum) {
        if(node == null) {
            return;
        }

        sum += node.val;

        if(targetSum == sum) {
            answer++;
        }

        DFS(node.left, sum, targetSum);
        DFS(node.right, sum, targetSum);
    }
}

• 각 노드를 root로해서 완전탐색 -> 합 계산