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package g0101_0200.s0113_path_sum_ii;

// #Medium #Depth_First_Search #Tree #Binary_Tree #Backtracking #Data_Structure_II_Day_16_Tree
// #2022_06_23_Time_1_ms_(100.00%)_Space_44.7_MB_(53.10%)

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

/*
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
/**
 * 113 - Path Sum II\.
 *
 * Medium
 *
 * Given the `root` of a binary tree and an integer `targetSum`, return _all **root-to-leaf** paths where the sum of the node values in the path equals_ `targetSum`_. Each path should be returned as a list of the node **values** , not node references_.
 *
 * A **root-to-leaf** path is a path starting from the root and ending at any leaf node. A **leaf** is a node with no children.
 *
 * **Example 1:**
 *
 * ![](https://assets.leetcode.com/uploads/2021/01/18/pathsumii1.jpg)
 *
 * **Input:** root = [5,4,8,11,null,13,4,7,2,null,null,5,1], targetSum = 22
 *
 * **Output:** [[5,4,11,2],[5,8,4,5]]
 *
 * **Explanation:** There are two paths whose sum equals targetSum: 5 + 4 + 11 + 2 = 22 5 + 8 + 4 + 5 = 22 
 *
 * **Example 2:**
 *
 * ![](https://assets.leetcode.com/uploads/2021/01/18/pathsum2.jpg)
 *
 * **Input:** root = [1,2,3], targetSum = 5
 *
 * **Output:** [] 
 *
 * **Example 3:**
 *
 * **Input:** root = [1,2], targetSum = 0
 *
 * **Output:** [] 
 *
 * **Constraints:**
 *
 * *   The number of nodes in the tree is in the range `[0, 5000]`.
 * *   `-1000 <= Node.val <= 1000`
 * *   `-1000 <= targetSum <= 1000`
**/
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);
    }
}




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