Java for LeetCode 113 Path Sum II

標籤：

Given a binary tree and a sum, find all root-to-leaf paths where each path‘s sum equals the given sum.

For example:
Given the below binary tree and sum = 22,

              5             /             4   8           /   /           11  13  4         /  \    /         7    2  5   1

return

[   [5,4,11,2],   [5,8,4,5]]

 

解題思路：

DFS，JAVA實現如下：

static public List<List<Integer>> pathSum(TreeNode root, int sum) {List<List<Integer>> list = new ArrayList<List<Integer>>();List<Integer> alist = new ArrayList<Integer>();if (root != null)dfs(alist,list, root, sum);return list;}public static void dfs(List<Integer> alist,List<List<Integer>> list, TreeNode root, int sum) {if (root.left == null && root.right == null) {if (sum == root.val) {alist.add(root.val);list.add(new ArrayList<Integer>(alist));alist.remove(alist.size() - 1);}return;}alist.add(root.val);if (root.left == null)dfs(alist,list, root.right, sum - root.val);else if (root.right == null)dfs(alist,list, root.left, sum - root.val);else {List<Integer> alistCopy = new ArrayList<Integer>(alist);dfs(alist,list, root.right, sum - root.val);alist=alistCopy;dfs(alist,list, root.left, sum - root.val);}}

 

Java for LeetCode 113 Path Sum II