剑指offer--二叉树中和为某一值的路径

题目描述

输入一颗二叉树和一个整数，打印出二叉树中结点值的和为输入整数的所有路径。路径定义为从树的根结点开始往下一直到叶结点所经过的结点形成一条路径。

二叉树的遍历，深度搜索DFS； 模板

import java.util.ArrayList;

public class 二叉树中和为某一值的路径 {
	static class TreeNode {
	    int val = 0;
	    TreeNode left = null;
	    TreeNode right = null;

	    public TreeNode(int val) {
	        this.val = val;
	    }
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		System.out.println("begin");
		TreeNode testnode = new TreeNode(10);
		testnode.left = new TreeNode(5);
		testnode.right = new TreeNode(12);
		testnode.left.left = new TreeNode(7);
		testnode.left.right = new TreeNode(4);

		ArrayList<ArrayList<Integer>> result1 = FindPath(testnode,22);
		for (int i = 0; i < result1.size(); i++) {
			for (int j = 0; j < result1.get(i).size(); j++) {
				System.out.print(result1.get(i).get(j)+" ");
			}
			System.out.println();
		}
	}

    public static ArrayList<ArrayList<Integer>> FindPath(TreeNode root,int target) {
		ArrayList<ArrayList<Integer>> result = new ArrayList<>();
    	ArrayList<Integer> savepath = new ArrayList<>();
    	if (root==null) {
			return result;
		}
    	FindPathme(root,target,savepath,result);
		return result;
    }

	private static void FindPathme(TreeNode root, int target, ArrayList<Integer> savepath, ArrayList<ArrayList<Integer>> result) {
		// TODO Auto-generated method stub
		if (target<0) {
			return;//路径和>target，不再搜索
		}else if ((target==root.val)&&(root.left==null)&&(root.right==null)) {
			//把savelist赋给temp
			ArrayList<Integer> temp = new ArrayList<>();
			for (int i = 0; i < savepath.size(); i++) {
				temp.add(savepath.get(i));
			}
			temp.add(root.val);
			result.add(temp);//当前节点路径和为target。加入result
			return;
		}
		savepath.add(root.val);// 把当前节点记录进入路径savepath
		target-=root.val;
		if (root.left!=null) {
			FindPathme(root.left, target, savepath,result);
		}
		if (root.right!=null) {
			FindPathme(root.right, target, savepath,result);
		}
		target+=root.val;
		savepath.remove(savepath.size() - 1);
	}
}