殊途同归

/*
题目思路:
使用Java Stream API实现同样的功能。利用递归函数和流来进行深度优先搜索，并收集所有路径。
*/

import java.util.*;
import java.util.stream.Collectors;

class Solution {
    public List<List<Integer>> allPathsSourceTarget(int[][] graph) {
        return dfs(graph, 0);
    }
    
    private List<List<Integer>> dfs(int[][] graph, int node) {
        if (node == graph.length - 1) {
            return Collections.singletonList(Collections.singletonList(node));
        }
        return Arrays.stream(graph[node])
            .mapToObj(next -> dfs(graph, next).stream()
                .map(path -> {
                    List<Integer> newPath = new ArrayList<>();
                    newPath.add(node);
                    newPath.addAll(path);
                    return newPath;
                })
                .collect(Collectors.toList()))
            .flatMap(Collection::stream)
            .collect(Collectors.toList());
    }
}