POJ 1094 Sorting It All Out（拓扑序列）

Sorting It All Out

大意：给你一些关系，输出拓扑序列，如果有环，讨论一下；如果有多种情况，讨论一下；如果那两种都不是，输出拓扑序列。

思路：没什么好说的，就是一个求拓扑序列。

#include <map>
#include <stack>
#include <queue>
#include <math.h>
#include <stdio.h>
#include <string.h>
#include <iostream>
#include <limits.h>
#include <algorithm>
#define LL long long
#define min(a,b) (a>b?b:a)
#define max(a,b) (a>b?a:b)
#define eps 1e-9
#define INF 0x3f3f3f3f
using namespace std;

int n, m;
int Map[30][30], dis[30], Ans[30], tem[30];

int Topo()
{
    stack<int>s;
    memcpy(tem, dis, sizeof(dis));
    for(int i = 0; i < n; i++)
    {
        if(!tem[i])
        {
            s.push(i);
        }
    }
    int cnt = 0;
    bool flag0 = false;
    while(!s.empty())
    {
        if(s.size() > 1)
        {
            flag0 = true;
        }
        int temp = s.top();
        Ans[cnt++] = temp;
        s.pop();
        for(int i = 0; i < n; i++)
        {
            if(Map[temp][i] && --tem[i] == 0)
            {
                s.push(i);
            }
        }
    }
    if(cnt != n)
    {
        return 1;
    }
    else if(flag0)
    {
        return 2;
    }
    return 0;
}

void Solve()
{
    while(~scanf("%d%d", &n, &m) && (n ||m))
    {
        bool flag1 = false, flag2 = false;
        memset(Map, 0, sizeof(Map));
        memset(dis, 0, sizeof(dis));
        for(int i = 1; i <= m; i++)
        {
            char str[3];
            scanf("%s", str);
            if(!flag1 &&!flag2)
            {
                if(Map[str[2]-'A'][str[0]-'A'] == 1)
                {
                    flag2 = true;
                    printf("Inconsistency found after %d relations.
", i);
                    continue;
                }
                if(!Map[str[0]-'A'][str[2]-'A'])
                {
                    Map[str[0]-'A'][str[2]-'A'] = 1;
                    dis[str[2]-'A']++;
                }
                int flag = Topo();
                if(!flag)
                {
                    printf("Sorted sequence determined after %d relations: ", i);
                    for(int j = 0; j < n; j++)
                    {
                        printf("%c", Ans[j]+'A');
                    }
                    printf(".
");
                    flag1 = true;
                }
                else if(flag == 1)
                {
                    printf("Inconsistency found after %d relations.
", i);
                    flag2= true;
                }
            }
        }
        if(!flag1 &&!flag2)
        {
            printf("Sorted sequence cannot be determined.
");
        }
    }
}

int main(void)
{
    Solve();

    return 0;
}