113. 路径总和 II

113. 路径总和 II - 力扣（LeetCode）

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/**
 * 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;
 *     }
 * }
 */

先序遍历
根 左右
class Solution {
    private List<List<Integer>> result = new ArrayList<>();
    private List<Integer> path = new ArrayList<>();
    int sum = 0;
    public List<List<Integer>> pathSum(TreeNode root, int targetSum) {

        dfs(targetSum, root);

        return result;

    }

    private void dfs(int targetSum, TreeNode node) {
        if(node == null){
            return;
        }
        //sum+=node.val;
        targetSum-=node.val;
        path.add(node.val);
       if (targetSum == 0 && node.left==null && node.right== null){
            result.add(new ArrayList<>(path));
        }        

        dfs(targetSum,node.left);
        dfs(targetSum,node.right);
        //sum-=node.val;
        targetSum+=node.val;
        path.remove(path.size()-1);

    }
}