java - 为什么返回值不等于数组？

Question

我正在进行深度优先搜索，但输出不等于数组。怎么了？

public static int[] Search (int [][] graph){
        boolean[] visited = {false, false, false, false, false, false};
        int n = 6;
        List<Integer> output = new ArrayList<>();
        Search(graph, visited, n, 0);
        return output.stream().mapToInt(Integer::intValue).toArray();
    }

    public static void Search(int[][] graph, boolean [] visited, int n, int i) {
        System.out.print((i )+" ");
        visited[i] = true;
        for (int j = 0; j < n; j++) {
            if (!(visited[j]) && graph[i][j] == 1) {
                Search(graph, visited, n, j);
            }
        }
    }

public static void main(String[] args) {

        int [][] graph={{0,1,1,1,0,0},{1,0,0,0,1,1},{1,0,0,0,0,1},{1,0,0,0,0,0},{0,1,0,0,0,0},{0,1,1,0,0,0}};

        int [] Searchresult={0,1,4,5,2,3};

    }   

如您所见，DFSresult 和输出是相同的。我的返回声明有误吗？

Answer 1

您的DFS(graph) 方法返回一个空数组:

List<Integer> output = new ArrayList<>();
DFS(graph, visited, n, 0);
return output.stream().mapToInt(Integer::intValue).toArray();

您永远不会向创建数组的 ArrayList 添加任何内容。

您可能忘记了将 output 列表传递给 void DFS(int[][] graph, boolean [] visited, int n, int i) 方法并为其添加值。

public static int[] DFS (int [][] graph) {
    boolean[] visited = {false, false, false, false, false, false};
    int n = 6;
    List<Integer> output = new ArrayList<>();
    DFS(graph, visited, n, 0, output);
    return output.stream().mapToInt(Integer::intValue).toArray();
}

public static void DFS(int[][] graph, boolean [] visited, int n, int i, List<Integer> output) {
    System.out.print((i )+" ");
    output.add(i);
    visited[i] = true;
    for (int j = 0; j < n; j++) {
        if (!(visited[j]) && graph[i][j] == 1) {
            DFS(graph, visited, n, j, output);
        }
    }
}

进行这些更改后，输出变为

0 1 4 5 2 3 DFS is working correctly