拓扑排序模板

拓扑排序是对ADG（有向无环图进行线性排序）

模板：

二维数组模拟链表

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
using namespace std;
int indegree[100];
queue<int> q;
int n,m;
bool map[100][100];
int a[100];
int topo(int n)
{
    int cnt = 1;
    while(!q.empty())
        q.pop();
    for(int i = 1; i <= n ; i++)
        if(indegree[i] == 0)
            q.push(i);
    int u;
    while(!q.empty()){
        u = q.front();
        a[cnt++] = u;
        q.pop();
        for(int i = 1; i <= n ; i++){
            if(map[u][i]){
                indegree[i] --;
                if(indegree[i] == 0)
                    q.push(i);
            }
        }
        if(cnt == n){
            for(int i = 1 ; i <= n ; i++)
                printf(" %d",a[i]);
        }
        else printf("The network has a cycle");
    }
}
int main()
{
    int u,v;
    while(~scanf("%d%d",&n,&m)){
        memset(indegree,0,sizeof(indegree));
        memset(map,0,sizeof(map));
        for(int i = 0 ; i < m ; i++){
            scanf("%d%d",&u,&v);
            if(!map[u][v])
                indegree[v]++;
                map[u][v] = 1;
        }
               topo(n);
    }
    return 0;
}

　　

邻接表实现

#include<cstring>
#include<algorithm>
#include<queue>
#include<vector>
using namespace std;
const int M = 100005;
int a[M];
int indegree[M];
int n,m,u,v;
vector<int> G[M];
void topo()
{
    memset(indegree,0,sizeof(indegree));
    memset(a,0,sizeof(a));
    for(int i = 1; i <= n ; i++){
        for(int j = 0 ; j <= G[i].size(); j++){
            indegree[G[i][j]]++;
        }
    }
    queue<int> q;
    while(!q.empty())
        q.pop();
    int cnt = 1;
    for(int i = 1;i <= n ; i++){
        if(!indegree[i])
            q.push(i);
    }
    while(!q.empty()){
        int u = q.front();
        q.pop();
        a[cnt++] = u;
        for(int i = 0 ; i <G[u].size(); i++){
            int v = G[u][i];
            indegree[v]--;
            if(!indegree[v])
                q.push(v);
        }
    }
    if(cnt == n){
        for(int i = 1; i < cnt; i++)
            printf(" %d", a[i]);
        printf("%d\n",a[cnt]);
    }
    else printf("This is a cycle\n");
}
int main()
{
    while(~scanf("%d%d",&n,&m)){
　　　　　for(int i = 1; i <= n ; i++)
　　　　　　G[i].clear();
        for(int i = 1; i <= m ; i++){
            scanf("%d%d",&u,&v);
            G[u].push_back(v);
        } 
        topo();
    }
    return 0;
}