g0101_0200.s0113_path_sum_ii.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated

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package g0101_0200.s0113_path_sum_ii;

// #Medium #Depth_First_Search #Tree #Binary_Tree #Backtracking
// #2022_02_22_Time_1_ms_(100.00%)_Space_42.4_MB_(47.38%)

import com_github_leetcode.TreeNode;
import java.util.ArrayList;
import java.util.List;

public class Solution {
    public List> pathSum(TreeNode root, int targetSum) {
        List> res = new ArrayList<>();
        if (root == null) {
            return res;
        }
        recur(res, new ArrayList<>(), 0, targetSum, root);
        return res;
    }

    private void recur(
            List> res, ArrayList al, int sum, int targetSum, TreeNode root) {
        if (root == null) {
            return;
        }
        al.add(root.val);
        sum += root.val;
        if (sum == targetSum && root.left == null && root.right == null) {
            res.add(new ArrayList<>(al));
        }
        recur(res, al, sum, targetSum, root.left);
        recur(res, al, sum, targetSum, root.right);
        al.remove(al.size() - 1);
    }
}