<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=0;int W=0;char ch=0;
    while(!isdigit(ch))W|=ch=='-',ch=getchar();
    while(isdigit(ch))X=(X<<3)+(X<<1)+(ch^48),ch=getchar();
    X=W?-X:X;return;
}
int n,m,head[30],CNT=0,in[30],IN[30],cnt=0,Cnt=0,vis[30],ans[30];
struct node{int to,next;}edge[50];
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=0,pd2=0;cnt=0;
    for(rint i=1;i<=26;++i)
    {
        IN[i]=in[i];
        if(!IN[i] && vis[i])
        {
            if(!pd)pd=1;
            else pd2=1;
            q.push(i);
            ans[++cnt]=i;
        }
    }
    if(q.empty())return 1;
    while(!q.empty())
    {
        int u=q.front();q.pop();pd=0;
        for(rint i=head[u];i;i=edge[i].next)
        {
            --IN[edge[i].to];
            
            if(!IN[edge[i].to])
            {
                if(!pd)pd=1;
                 else pd2=1;
                q.push(edge[i].to);
                ans[++cnt]=edge[i].to;
            }
        }
    }
    if(cnt!=CNT)return 1;
    if(pd2)return 2;
    return 0;
}
int main()
{
    read(n),read(m);
    for(rint i=1;i<=m;++i)
    {
        char a[5];
        scanf("%s",a); 
        int u=a[0]-64,v=a[2]-64;
        add(u,v);
        if(!vis[u])vis[u]=1,CNT++;
        if(!vis[v])vis[v]=1,CNT++;
        int tps=tp();
        if(tps==1)
        {
            printf("Inconsistency found after %d relations.",i);
            return 0;
        }
        if(cnt==n && !tps)
        {
            printf("Sorted sequence determined after %d relations: ",i);
            for(rint j=1;j<=cnt;++j)printf("%c",ans[j]+64);
            printf(".") ;
            return 0;
        }
    }
    printf("Sorted sequence cannot be determined.");
return 0;
}