<luogu1347>排序

本来打算当打了个拓扑的板子

后来发现并不只是个板子

差不多 管他呢

#include<cstdio>
#include<cstring>
#include<iostream>
#include<queue>
#include<algorithm>
#define rint register int
using std::queue;
using std::cout;
using std::endl;
template <class T> inline void read(T &X)
{
    X=;int W=;char ch=;
    while(!isdigit(ch))W|=ch=='-',ch=getchar();
    while(isdigit(ch))X=(X<<)+(X<<)+(ch^),ch=getchar();
    X=W?-X:X;return;
}
int n,m,head[],CNT=,in[],IN[],cnt=,Cnt=,vis[],ans[];
struct node{int to,next;}edge[];
queue<int> q;
void add(int u,int v)
{
    ++in[v];
    edge[++Cnt].to=v;
    edge[Cnt].next=head[u];
    head[u]=Cnt;
}

int tp()
{
    int pd=,pd2=;cnt=;
    for(rint i=;i<=;++i)
    {
        IN[i]=in[i];
        if(!IN[i] && vis[i])
        {
            if(!pd)pd=;
            else pd2=;
            q.push(i);
            ans[++cnt]=i;
        }
    }
    if(q.empty())return ;
    while(!q.empty())
    {
        int u=q.front();q.pop();pd=;
        for(rint i=head[u];i;i=edge[i].next)
        {
            --IN[edge[i].to];

            if(!IN[edge[i].to])
            {
                if(!pd)pd=;
                 else pd2=;
                q.push(edge[i].to);
                ans[++cnt]=edge[i].to;
            }
        }
    }
    if(cnt!=CNT)return ;
    if(pd2)return ;
    return ;
}
int main()
{
    read(n),read(m);
    for(rint i=;i<=m;++i)
    {
        char a[];
        scanf("%s",a);
        int u=a[]-,v=a[]-;
        add(u,v);
        if(!vis[u])vis[u]=,CNT++;
        if(!vis[v])vis[v]=,CNT++;
        int tps=tp();
        if(tps==)
        {
            printf("Inconsistency found after %d relations.",i);
            return ;
        }
        if(cnt==n && !tps)
        {
            printf("Sorted sequence determined after %d relations: ",i);
            for(rint j=;j<=cnt;++j)printf("%c",ans[j]+);
            printf(".") ;
            return ;
        }
    }
    printf("Sorted sequence cannot be determined.");
return ;
}