poj1094 Sorting It All Out

拓扑排序，好麻烦的说

code

/*
ID: yueqiq
PROG: numtri
LANG: C++
*/
#include <set>
#include <map>
#include <ctime>
#include <queue>
#include <cmath>
#include <stack>
#include <limits>
#include <vector>
#include <bitset>
#include <string>
#include <cstdio>
#include <cstring>
#include <fstream>
#include <string.h>
#include <iostream>
#include <algorithm>
#define Si set<int>
#define LL long long
#define pb push_back
#define PS printf(" ")
#define Vi vector<int>
#define LN printf("\n")
#define lson l,m,rt << 1
#define rson m+1,r,rt<<1|1
#define SD(a) scanf("%d",&a)
#define PD(a) printf("%d",a)
#define SET(a,b) memset(a,b,sizeof(a))
#define FF(i,a) for(int i(0);i<(a);i++)
#define FD(i,a) for(int i(a);i>=(1);i--)
#define FOR(i,a,b) for(int i(a);i<=(b);i++)
#define FOD(i,a,b) for(int i(a);i>=(b);i--)
#define readf freopen("input.txt","r",stdin)
#define writef freopen("output.txt","w",stdout)
const int maxn = 102;
const int INF = 0x3fffffff;
const int dx[]={0,1,0,-1};
const int dy[]={1,0,-1,0};
const double pi = acos(-1.0);
const double eps= 1e-7;
using namespace std;
//A=0,B=1,........
int N,M;
int indegree[26];
bool link[26][26];
int path[26],cnt;
int topsort(){
    int zero_cnt=0;
    int zeronode;
    int in[26];
    FF(i,26){ in[i]=indegree[i];
        //printf(" i:%d  in:%d\n",i,in[i]);
    }
    bool flag=false;
    cnt=0;
    SET(path,0);
    FF(i,N){
//        puts("--------------------------");
//        FF(j,N){
//            printf(" i:%d  in:%d\n",j,in[j]);
//        }
//        puts("--------------------------");
        zero_cnt=0;
        FF(j,N){
            if(in[j]==0){
                zero_cnt++;
                zeronode=j;
                //PD(j);LN;
            }
        }
        //printf("zerocnt: %d  zeronode:%d \n",zero_cnt,zeronode);
        if(zero_cnt==0) return -1;//loop occur;
        if(zero_cnt>1) flag=true;//ambigous
        in[zeronode]=-1;
        FF(j,N){
            if(link[zeronode][j])
                in[j]--;
        }
        path[cnt++]=zeronode;
    }
    if(flag) return 1;
    return 0;
}
int main()
{
    char t[3];
    int a,b;
    while(~scanf("%d%d",&N,&M)&&(N+M)){
        SET(link,false);SET(indegree,0);
        int k=1,step=1;
        FOR(i,1,M){
            scanf("%s",t);
            a=t[0]-'A';
            b=t[2]-'A';
            indegree[b]++;
            link[a][b]=true;
            if(k==1){
                k=topsort();
                step=i;
            }
            //PD(k);LN;
        }
        if(k==0){
            printf("Sorted sequence determined after %d relations: ",step);
            FF(i,cnt){
                printf("%c",(char)(path[i]+'A'));
            }
            puts(".");
        }else if(k==-1){
            printf("Inconsistency found after %d relations.\n",step);
        }else{
            puts("Sorted sequence cannot be determined.");
        }
    }
    return 0;
}