LeetCode | Path Sum II

题目

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

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

return

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

这题直接用递归写，类似DFS。

代码

import java.util.ArrayList;

public class PathSumII {
	public class TreeNode {
		int val;
		TreeNode left;
		TreeNode right;

		TreeNode(int x) {
			val = x;
		}
	}

	private ArrayList<ArrayList<Integer>> results;

	public ArrayList<ArrayList<Integer>> pathSum(TreeNode root, int sum) {
		results = new ArrayList<ArrayList<Integer>>();
		ArrayList<Integer> list = new ArrayList<Integer>();
		solve(root, sum, list);
		return results;
	}

	private void solve(TreeNode root, int sum, ArrayList<Integer> list) {
		if (root == null) {
			return;
		}

		list.add(root.val);
		if (sum == root.val && root.left == null && root.right == null) {
			results.add(new ArrayList<Integer>(list));
		} else {
			solve(root.left, sum - root.val, list);
			solve(root.right, sum - root.val, list);
		}
		list.remove(list.size() - 1);
	}
}

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LeetCode | Path Sum II

原文：http://blog.csdn.net/perfect8886/article/details/20006145