一 拓扑图

二 实现

package graph.topoSort;

import java.util.Scanner;
import java.util.Stack;

public class TopoSort {
    static final int maxn = 105;
    static int map[][] = new int[maxn][maxn];
    static int indegree[] = new int[maxn];
    static int topo[] = new int[maxn];
    static int n, m;
    static Stack<Integer> s = new Stack<>();

    static boolean TopoSort() { // 拓扑排序
        int cnt = 0;
        for (int i = 0; i < n; i++)
            if (indegree[i] == 0)
                s.push(i);
        while (!s.empty()) {
            int u = s.peek();
            s.pop();
            topo[cnt++] = u;
            for (int j = 0; j < n; j++)
                if (map[u][j] == 1)
                    if (--indegree[j] == 0)
                        s.push(j);
        }
        if (cnt < n) {
            return false;
        }
        return true;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        n = scanner.nextInt();
        m = scanner.nextInt();

        for (int i = 0; i < m; i++) {
            int u, v;
            u = scanner.nextInt();
            v = scanner.nextInt();
            map[u][v] = 1;
            indegree[v]++;
        }
        TopoSort();
        for (int i = 0; i < n - 1; i++)
            System.out.print(topo[i] + " ");
        System.out.println(topo[n - 1]);
    }
}

三 测试