題目：輸入一棵二叉樹和一個整數， 打印出二叉樹中結點值的和為輸入整數的所有路徑。從樹的根結點開始往下一直到葉結點所經過的結點形成一條路徑。

import java.util.ArrayList;

public class FindPath {
    ArrayList<Integer> path = new ArrayList<>();
    ArrayList<ArrayList<Integer>> list = new ArrayList<>();
    public ArrayList<ArrayList<Integer>> findPath
 
(TreeNode root,int target) {
        if (root==null){
            return list;
        }
        path.add(root.val);
        target = target- root.val;
        if(target==0 && root.left==null && root.right == null){
            list.add(new ArrayList<Integer>(path));

        }
        findPath(root.left, target);
        findPath(root.right, target);

        path.remove(path.size()-1
 
);
        return list;

    }

    public static void main(String[] args) {
        TreeNode a = new TreeNode(0);
        TreeNode b = new TreeNode(1);
        TreeNode c = new TreeNode(2);
        TreeNode d = new TreeNode(3);
        TreeNode e = new TreeNode(4);
        TreeNode f = new TreeNode(5
 
);
        TreeNode g = new TreeNode(6);
        a.left=b;
        a.right=c;
        b.left=d;
        b.right=e;
        c.left=f;
        c.right=g;
        FindPath find = new FindPath();
        ArrayList<ArrayList<Integer>> list = new ArrayList<ArrayList<Integer>>();
        list = find.findPath(a, 7);
        for( ArrayList<Integer> path:list ){
            for(Integer item: path){
                System.out.print(item +" ");
            }
            System.out.println();
        }

    }

}

class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;
    }
 }

列印二叉樹的路徑

import java.util.ArrayList;

public class FindPath1 {
    ArrayList<Integer> path = new ArrayList<>();
    ArrayList<ArrayList<Integer>> list = new ArrayList<>();
    public ArrayList<ArrayList<Integer>> findPath(TreeNode root) {

        if (root==null){
            return list;
        }
        path.add(root.val);

        if(root.left==null && root.right == null){
            list.add(new ArrayList<Integer>(path)); 
        }
        findPath(root.left);
        findPath(root.right);
        path.remove(path.size()-1);
        return list;

    }

    public static void main(String[] args) {
        TreeNode a = new TreeNode(0);
        TreeNode b = new TreeNode(1);
        TreeNode c = new TreeNode(2);
        TreeNode d = new TreeNode(3);
        TreeNode e = new TreeNode(4);
        TreeNode f = new TreeNode(5);
        TreeNode g = new TreeNode(6);
        a.left=b;
        a.right=c;
        b.left=d;
        b.right=e;
        c.left=f;
        c.right=g;
        FindPath1 find = new FindPath1();
        ArrayList<ArrayList<Integer>> list = new ArrayList<ArrayList<Integer>>();
        list = find.findPath(a);
        for( ArrayList<Integer> path:list ){
            for(Integer item: path){
                System.out.print(item +" ");
            }
            System.out.println();
        }

    }

}

class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;
    }
 }