Hoj 1336/Poj 1094 Sorting It All Out

题目：http://acm.hit.edu.cn/hoj/problem/view?id=1336

http://poj.org/problem?id=1094

本题联系拓扑排序。

如果给定的所有偏序关系中，能求得唯一的拓扑排序，则输出：Sorted sequence determined after xxx relations: yyy...y. 

如果有环，则输出：Inconsistency found after xxx relations. 

如果有不止一个拓扑序，则输出：Sorted sequence cannot be determined.

由于需要记录下在第几个偏序关系中能得出结论，所以每读入一个偏续就需要进行一次排序判断，toposort()可以作为拓扑排序的模板。

#include <iostream>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <math.h>#include <algorithm>#include <stack>#include <queue>#include <string>using namespace std;int map[30][30];int indegree[30];int n,m;queue<int> q;queue<int> record;//拓扑排序int toposort(){    //清空队列    while(!q.empty())    {        q.pop();    }    while(!record.empty())    {        record.pop();    }    int in[30];    memcpy(in,indegree,sizeof(indegree));    for(int i=0;i<n;i++)    {        if(in[i] == 0)        {            q.push(i);        }    }    int flag = 0;    while(!q.empty())    {        int a = q.front();        record.push(a);        q.pop();        if(!q.empty())        {            flag = 1;        }        for(int i=0;i<n;i++)        {            if(map[a][i] == 1)            {                in[i]--;                if(in[i] == 0)                {                    q.push(i);                }            }        }    }    //有环路    if(record.size()!=n)    {        return 0;    }    //不确定排序方式    else if(flag == 1)    {        return 1;    }    return 2;//有唯一拓扑}int main(){#ifndef ONLINE_JUDGE    freopen("in.txt","r",stdin);#endif    while(scanf(" %d %d",&n,&m)!=EOF && n!=0 && m!=0)    {        memset(map,0,sizeof(map));        memset(indegree,0,sizeof(indegree));        int flag = 0;        for(int i=0;i<m;i++)        {            char a,b;            scanf(" %c<%c",&a,&b);            if(map[b-'A'][a-'A'] == 1)            {                flag = 1;                printf("Inconsistency found after %d relations.\n",i+1);                for(int j=i+1;j<m;j++)                {                    scanf(" %c<%c",&a,&b);                }                break;            }            else if(map[a-'A'][b-'A'] == 0)            {                map[a-'A'][b-'A'] = 1;                indegree[b -'A']++;            }            int res = toposort();            if(res == 0)            {                flag = 1;                printf("Inconsistency found after %d relations.\n",i+1);                for(int j=i+1;j<m;j++)                {                    scanf(" %c<%c",&a,&b);                }                break;            }            else if(res == 2)            {                flag = 1;                for(int j=i+1;j<m;j++)                {                    scanf(" %c<%c",&a,&b);                }                printf("Sorted sequence determined after %d relations: ",i+1);                while(!record.empty())                {                    int top = record.front();                    record.pop();                    printf("%c",top + 'A');                }                printf(".\n");                break;            }        }        if(flag == 0)        {            printf("Sorted sequence cannot be determined.\n");        }    }    return 0;}