POJ 1094

#include<iostream>
#include<stdio.h>
#include<algorithm>
#define MAXN 30
using namespace std;

char upper[MAXN];
bool rel[MAXN][MAXN];
int n;

void update();
int count();
void sort_upper();
int main()
{
    //freopen("acm.acm","r",stdin);
    int m;
    char c_1;
    char c_2;
    char op;
    int i;
    int j;
    bool inco;
    bool sort;
    int time;
    int sort_num;
    while(cin>>n>>m)
    {
        if(!n && ! m)
            break;
        memset(rel,false,sizeof(rel) );
        for(char a = 'A'; a <= 'Z'; ++ a)
        {
            upper[a-'A'] = a;
        }
        
        inco = false;
        sort = false;
        for(i = 0; i < m; ++ i)
        {
            cin>>c_1>>op>>c_2;
            if(inco || sort)
                continue;
            rel[c_1 - 'A'][c_2 - 'A'] = true;
            if(rel[c_2 - 'A'][c_1 - 'A'] == true)
            {
                inco = true;
                time = i+1;
                continue;
            }
            update();
            sort_num = count();
        //    cout<<sort_num<<endl;
        //    cout<<i<<endl;
            if(sort_num == n * (n - 1) / 2
                )
            {
                sort = true;
                time = i+1;
                continue;
            }
        }
        if(inco)
        {
            cout<<"Inconsistency found after "<<time<<" relations."<<endl;
        }
        else if(sort)
        {
            sort_upper();
            cout<<"Sorted sequence determined after "<<time<<" relations: ";
            for(i = 0; i < n; ++ i)
            {
                cout<<upper[i];
            }
            cout<<"."<<endl;
        }
        else
        {
            cout<<"Sorted sequence cannot be determined."<<endl;
        }
    }
}


void update()
{
    int i;
    int j;
    int k;
    for(k = 0; k < n; ++ k)
    {
        for(i = 0; i < n; ++ i)
        {
            for(j = 0; j < n; ++ j)
            {
                if(rel[i][k] && rel[k][j])
                    rel[i][j] = true;
            }
        }
    }
}

int count()
{
    int ans = 0;
    int i;
    int j;
    for(i = 0; i < n; ++ i)
    {
        for(j = 0; j < n; ++ j)
        {
            if(rel[i][j])
                ++ ans;
        }
    }
    return ans;
}

void sort_upper()
{
    int i;
    int j;
    for(i = 0; i < n; ++ i)
    {
        for(j = i + 1; j < n; ++ j)
        {
            if(rel[upper[j] - 'A'][upper[i] - 'A'])
            {
                iter_swap(&upper[i],&upper[j]);
            }
        }
    }
}

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