滴滴笔试题-集合DFS

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import java.util.*;

public class Main {
    public static boolean isReachable(List<Integer>[] g, int a, int b, boolean[] seen) {
        seen[a] = true;
        boolean tmp = false;
        for (int i : g[a]) {
            if (i == b) {
                tmp = true;
            } else {
                if (!seen[i]) {
                    tmp = tmp || isReachable(g, i, b, seen);
                }
            }
        }
        return tmp;
    }

    public static int position(List<Integer> ls, int a) {
        for (int i = 0; i < ls.size(); i++) {
            if (ls.get(i) == a) {
                return i;
            }
        }
        return -1;
    }

    public static void show(List<Integer>[] g) {
        System.out.println();
        for (int i = 0; i < g.length; i++) {
            System.out.println("g[" + i + "]: " + g[i]);
        }
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int count = sc.nextInt();
        sc.nextLine();
        String[] nAndM = sc.nextLine().trim().split(" ");
        int N = Integer.valueOf(nAndM[0]);
        int M = Integer.valueOf(nAndM[1]);
        List<Integer>[] g = new ArrayList[M];
        for (int i = 0; i < N; i++) {
            g[i] = new ArrayList<Integer>();
        }
        int[][] edges = new int[M][2];
        for (int i = 0; i < M; i++) {
            String[] edge = sc.nextLine().trim().split(" ");
            edges[i][0] = Integer.valueOf(edge[0]) - 1;
            edges[i][1] = Integer.valueOf(edge[1]) - 1;
            g[Integer.valueOf(edge[0]) - 1].add(Integer.valueOf(edge[1]) - 1);
            g[Integer.valueOf(edge[1]) - 1].add(Integer.valueOf(edge[0]) - 1);
        }
        // System.out.println();
        // for (int i = 0; i < M; i++) {
        // System.out.println(edges[i][0]+" "+edges[i][1]);
        // }
        boolean flag = true;
        boolean[] seen = new boolean[N];
        for (int[] e : edges) {
            boolean is_tmp = false;
            g[e[0]].remove(position(g[e[0]], e[1]));
            g[e[1]].remove(position(g[e[1]], e[0]));
            show(g);
            for (int i = 1; i < N; i++) {
                is_tmp = isReachable(g, 0, i, seen);
                // System.out.println("i:" + i + "-->" + is_tmp);
                if (!is_tmp) {
                    flag = false;
                    System.out.println("No");
                    System.exit(0);
                } else {
                    for (int j = 0; j < N; j++) {
                        seen[j] = false;
                    }
                }
            }
            g[e[0]].add(e[1]);
            g[e[1]].add(e[0]);
        }
        if (flag) {
            System.out.println("Yes");
        }
    }
}

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