拓扑排序

#include<iostream> 
#include<cstdio>
#include<cmath>
#include<cstring>
using namespace std;
int m,n,list[101],p=0,head[101],indgr[101],edgenum;//indgr:入度 
struct node{int next,to;} edge[101];
int stack[101],top=0;
void push(int d){stack[++top]=d;}
int pop(){return stack[top--];}
void add(int x,int y)
{
    edgenum++;
    edge[edgenum].to=y;
    edge[edgenum].next=head[x];
    head[x]=edgenum;
    indgr[y]++;
}
void rm(int en)//edgenum
{
    edgenum--;
    indgr[edge[en].to]--;
    if(!indgr[edge[en].to])
        push(edge[en].to);
    if(edge[en].next)
        rm(edge[en].next);
}
void read()
{
    cin >> n >> m;
    int u, v;
    for (int i = 1; i <= m; i++)
    {
            cin >> u >> v;
            add(u, v);
    }
}
void work()
{
    //初始化stack 
    for(int i=1;i<=n;i++)
        if(!indgr[i])
            push(i);
    while(top>0)
    {
        list[++p]=pop();
        rm(head[list[p]]);
    }
    if(!edgenum)
        cout<<"Circle";
    else for(int i=1;i<=p;i++) cout<<list[i];
}
int main()
{
    freopen("tppx.in", "r", stdin);
    read();
    work();
    return 0;
}