POJ 1094 Sorting It All Out（拓扑排序+判环+拓扑路径唯一性确定）

#include<stdio.h>
#include<iostream>
#include<math.h>
#include<string.h>
#include<set>
#include<map>
#include<list>
#include<queue>
#include<algorithm>
using namespace std;
typedef long long LL;
int mon1[13]= {0,31,28,31,30,31,30,31,31,30,31,30,31};
int mon2[13]= {0,31,29,31,30,31,30,31,31,30,31,30,31};
int dir[4][2]= {{0,1},{0,-1},{1,0},{-1,0}};

int getval()
{
    int ret(0);
    char c;
    while((c=getchar())==‘ ‘||c==‘\n‘||c==‘\r‘);
    ret=c-‘0‘;
    while((c=getchar())!=‘ ‘&&c!=‘\n‘&&c!=‘\r‘)
        ret=ret*10+c-‘0‘;
    return ret;
}

#define max_v 55
int indgree[max_v];
int temp[max_v];
int G[max_v][max_v];
int tp[max_v];
int n,m;
queue<int> q;
int tpsort()
{
    while(!q.empty())
        q.pop();
    for(int i=1;i<=n;i++)
    {
        indgree[i]=temp[i];
        if(indgree[i]==0)
            q.push(i);
    }

    int c=0,p;
    int flag=0;
    while(!q.empty())
    {
        if(q.size()>1)
            flag=1;
        p=q.front();
        q.pop();
        tp[++c]=p;
        for(int i=1;i<=n;i++)
        {
            if(G[p][i])
            {
                indgree[i]--;
                if(indgree[i]==0)
                    q.push(i);
            }
        }
    }
    /*
    拓扑完之后，存在没有入队的点，那么该点就一定是环上的
    */
    if(c!=n)//存在环 
        return 1;
    else if(flag)//能拓扑但存在多条路
        return 0;
    return -1;//能拓扑且存在唯一拓扑路径
}
int main()
{
    int x,y;
    char c1,c2;
    while(~scanf("%d %d",&n,&m))
    {
        if(n==0&&m==0)
            break;
        memset(G,0,sizeof(G));
        memset(temp,0,sizeof(temp));
        memset(tp,0,sizeof(tp));
        int flag1=0,index1=0;//是否有环及环的位置
        int flag2=0,index2=0;//能否拓扑和拓扑的位置
        for(int i=1;i<=m;i++)
        {
            getchar();
            scanf("%c<%c",&c1,&c2);
            x=c1-‘A‘+1;
            y=c2-‘A‘+1;
            if(flag1==0&&flag2==0)
            {
                if(G[y][x])//环的一种情况
                {
                    flag1=1;
                    index1=i;
                    continue;
                }
                if(G[x][y]==0)//预防重边
                {
                    G[x][y]=1;
                    temp[y]++;
                }
                int k=tpsort();
                if(k==1)//存在环
                {
                    flag1=1;
                    index1=i;
                    continue;
                }else if(k==-1)//存在唯一拓扑路径
                {
                    flag2=1;
                    index2=i;
                }
            }
        }
        if(flag1==0&&flag2==0)
        {
            printf("Sorted sequence cannot be determined.\n");
        }else if(flag1)
        {
            printf("Inconsistency found after %d relations.\n",index1);
        }else if(flag2)
        {
            printf("Sorted sequence determined after %d relations: ",index2);
            for(int i=1;i<=n;i++)
            {
                printf("%c",tp[i]+‘A‘-1);
            }
            printf(".\n");//！！！注意还有个点...
        }
    }
    return 0;
}