[POJ 1094] Sorting It All Out

[题目链接]

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

[算法]

         floyed传递闭包

[代码]

          

#include <algorithm>  
#include <bitset>  
#include <cctype>  
#include <cerrno>  
#include <clocale>  
#include <cmath>  
#include <complex>  
#include <cstdio>  
#include <cstdlib>  
#include <cstring>  
#include <ctime>  
#include <deque>  
#include <exception>  
#include <fstream>  
#include <functional>  
#include <limits>  
#include <list>  
#include <map>  
#include <iomanip>  
#include <ios>  
#include <iosfwd>  
#include <iostream>  
#include <istream>  
#include <ostream>  
#include <queue>  
#include <set>  
#include <sstream>  
#include <stdexcept>  
#include <streambuf>  
#include <string>  
#include <utility>  
#include <vector>  
#include <cwchar>  
#include <cwctype>  
#include <stack>  
#include <limits.h>
using namespace std;
#define MAXC 30

int i,j,k,n,m,pos;
int cnt[30];
int d[MAXC][MAXC];
char a,b;
bool flag;

int main() 
{
        
        while(scanf("%d%d
",&n,&m) != EOF && n)
        {
                pos = 0;
                memset(d,0,sizeof(d));
                for (i = 1; i <= n; i++) d[i][i] = 1;
                for (i = 1; i <= m; i++)
                {
                        scanf("%c<%c
",&a,&b);
                      d[a - 'A' + 1][b - 'A' + 1] = 1;    
                        for (j = 1; j <= n; j++)
                        {
                                for (k = 1; k <= n; k++)
                                {
                                        d[j][k] |= d[j][a - 'A' + 1] & d[b - 'A' + 1][k];
                                }
                        }
                        flag = true;
                        for (j = 1; j <= n; j++)
                        {
                                for (k = j + 1; k <= n; k++)
                                {
                                        if (d[j][k] && d[k][j])
                                        {
                                                if (!pos) pos = i;
                                                break;
                                        }
                                        if (!d[j][k] && !d[k][j]) 
                                        {
                                                flag = false;
                                                break;
                                        }
                                }
                                if (pos) break;
                        }
                        if (flag && !pos)
                        {
                                printf("Sorted sequence determined after %d relations: ",i);
                                memset(cnt,0,sizeof(cnt));
                                for (j = 1; j <= n; j++)
                                {
                                        for (k = 1; k <= n; k++)
                                        {
                                                if (j != k) cnt[j] += d[j][k];
                                        }
                                }
                                for (j = n - 1; j >= 0; j--)
                                {
                                        for (k = 1; k <= n; k++)
                                        {
                                                if (cnt[k] == j)
                                                        printf("%c",k + 'A' - 1);
                                        }
                                }
                                printf(".
");
                                i++;
                                for (i; i <= m; i++) scanf("%c<%c
",&a,&b);
                                break;
                        }
                }                
                if (flag && !pos) continue;
                else if (pos) printf("Inconsistency found after %d relations.
",pos);
                else printf("Sorted sequence cannot be determined.
");
        }
        
        return 0;
    
}