leetcode: path-sum-ii

题目描述:

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

For example: Given the below binary tree andsum = 22,

  5
  / \
 4  8
 / / \
 11 13 4
 / \     \
7 27   1

return

[
 [5,4,11,2],
 [5,8,4,5]
]

解题思路：

1. 这道题与上一题解题思路一致，需要注意的地方是因为要利用函数自身来递归，所以设置全局变量

代码如下：

    ArrayList<ArrayList<Integer>> res = new ArrayList<>();
    ArrayList<Integer> templist = new ArrayList<>();
    public ArrayList<ArrayList<Integer>> pathSum(TreeNode root, int sum) {
       if(root == null) return res;

       sum -= root.val;
       templist.add(root.val);

       if(sum == 0 && root.left == null && root.right == null){
           res.add(new ArrayList<>(templist));
       }
       else{
           pathSum(root.left,sum);
           pathSum(root.right, sum);
       }

       templist.remove(templist.size() - 1);

        return res;
    }

转载于:https://my.oschina.net/happywe/blog/3089834