#include <bits/stdc++.h>
using namespace std;
bool g[26][26]={0};
map <char,int> in;
map <char,int> tmp_in;
vector <char> waiting;
char result[26]={0};
int pos=0;
int n,m;
void prtg(){for (int i=0;i<n;i++){for (int j=0;j<n;j++){printf("%d ",g[i][j]);}printf("\n");}printf("\n");}
void prtin(){for (map<char,int>::iterator iter=in.begin();iter!=in.end();iter++)cout<<iter->first<<':'<<iter->second<<endl;}
void prttmpin(){for (map<char,int>::iterator iter=tmp_in.begin();iter!=tmp_in.end();iter++)cout<<iter->first<<':'<<iter->second<<endl;}
int slove()
{
    waiting.clear();
    //prttmpin();
    if (tmp_in.empty()) return 1;
    for (map<char,int>::iterator iter=tmp_in.begin();iter!=tmp_in.end();iter++)
        if (iter->second==0)
        {
            waiting.push_back(iter->first);
        }
    //if (!waiting.empty()) {for (vector <char>::iterator iter=waiting.begin();iter!=waiting.end();iter++) cout<<*iter;cout<<endl;}
    if (waiting.empty())
    {
            return -1;
    }
    else if (waiting.size()>1) return 0;
    else
    {
        tmp_in.erase(waiting.front());
        result[pos++]=waiting.front();
        for (int i=0;i<n;i++)
        {
            if (g[waiting.front()-'A'][i])
                tmp_in.at('A'+i)--;
        }
        return slove();
    }
}
int main(void)
{
    waiting.clear();
    pos=0;
    cin>>n>>m;
    char c1,c2;
    for (int i=0;i<n;i++)
        in.insert({'A'+i,0});
    for (int i=1;i<=m;i++)
    {
        //printf("read in relation %d\n",i);
        int cnt=0,pos=0;
        getchar();
        cin>>c1;
        getchar();
        cin>>c2;
        if (c1==c2)
        {
            printf("Inconsistency found after %d relations.",i);
            return 0;
        }
        if(!g[c1-'A'][c2-'A'])
        {
            g[c1-'A'][c2-'A']=1;
            in.at(c2)++;
        }
        //prtg();prtin();
        tmp_in=in;
        switch (slove())
        {
            case 1:printf("Sorted sequence determined after %d relations: %s.",i,result);return 0;break;
            case 0:continue;break;
            case -1:printf("Inconsistency found after %d relations.",i);return 0;break;
        }
    }
    printf("Sorted sequence cannot be determined.");
    return 0;
}

思路和题解是一样的，三组测试数据也过了，还是好几个WA，求助