POJ

题解：如果a

#include<iostream>#include<cstring>#include<cstdio>#include<cstring>#include<queue>using namespace std;#define x b-'A'#define y c-'A'int a[30];int n,m;int g[30][30];int in[30];int sum[30];int vis[30];queue<int>q;int so1 = 0,so2 = 0;int solve(char b,char c){    if(!g[x][y]){        g[x][y] = 1;        in[y]++;    }    memset(sum,0,sizeof(sum));    int cnt = 0,ok = 1;    for(int i = 0; i < n; i++)        if(sum[i]==in[i]){            q.push(i);            cnt++;            a[i] = 1;        }    while(!q.empty()){        int u = q.front();        q.pop();        if(!q.empty())            ok = 0;      //  cout<<u<<endl;;        for(int v = 0; v < n; v++)            if(g[u][v]){                sum[v]++;                if(sum[v]==in[v]){                    a[v] = a[u]+1;                    q.push(v);                    cnt++;                }            }    }    //cout<<cnt<<endl;    if(cnt!=n)        return 2;    if(ok)        return 1;    return 0;}int main(){    char s[30];    char str[30];    while(scanf("%d%d",&n,&m)&&n+m){        for(int i = 0; i < n; i++)            a[i] = 1;        so1 = 0,so2 = 0;        memset(g,0,sizeof(g));        memset(in,0,sizeof(in));        int ans;        for(int i = 1; i <= m; i++){            scanf("%s",s);            if(so1||so2)                continue;            if(a[s[0]-'A']<a[s[0]-'A'])                continue;            if(s[1]=='<')                ans = solve(s[0],s[2]);            else                ans = solve(s[2],s[0]);            if(ans==1&&!so1)                so1 = i;            if(ans == 2&&!so2)                so2 = i;        }        if(so2)            printf("Inconsistency found after %d relations.\n",so2);        else if(so1){            printf("Sorted sequence determined after %d relations: ",so1);            for(int i = 0; i < n; i++)                    str[a[i]] = 'A'+i;            for(int i = 1; i <= n; i++)                    putchar(str[i]);            puts(".");        }        else                printf("Sorted sequence cannot be determined.\n");    }    return 0;}