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。

 

  1 #include <map>
  2 #include <stack>
  3 #include <queue>
  4 #include <math.h>
  5 #include <stdio.h>
  6 #include <string.h>
  7 #include <iostream>
  8 #include <limits.h>
  9 #include <algorithm>
 10 #define LL long long
 11 #define min(a,b) (a>b?b:a)
 12 #define max(a,b) (a>b?a:b)
 13 #define eps 1e-9
 14 #define INF 0x3f3f3f3f
 15 using namespace std;
 16 
 17 int n, m;
 18 int Map[30][30], dis[30], Ans[30], tem[30];
 19 
 20 int Topo()
 21 {
 22     stack<int>s;
 23     memcpy(tem, dis, sizeof(dis));
 24     for(int i = 0; i < n; i++)
 25     {
 26         if(!tem[i])
 27         {
 28             s.push(i);
 29         }
 30     }
 31     int cnt = 0;
 32     bool flag0 = false;
 33     while(!s.empty())
 34     {
 35         if(s.size() > 1)
 36         {
 37             flag0 = true;
 38         }
 39         int temp = s.top();
 40         Ans[cnt++] = temp;
 41         s.pop();
 42         for(int i = 0; i < n; i++)
 43         {
 44             if(Map[temp][i] && --tem[i] == 0)
 45             {
 46                 s.push(i);
 47             }
 48         }
 49     }
 50     if(cnt != n)
 51     {
 52         return 1;
 53     }
 54     else if(flag0)
 55     {
 56         return 2;
 57     }
 58     return 0;
 59 }
 60 
 61 void Solve()
 62 {
 63     while(~scanf("%d%d", &n, &m) && (n ||m))
 64     {
 65         bool flag1 = false, flag2 = false;
 66         memset(Map, 0, sizeof(Map));
 67         memset(dis, 0, sizeof(dis));
 68         for(int i = 1; i <= m; i++)
 69         {
 70             char str[3];
 71             scanf("%s", str);
 72             if(!flag1 &&!flag2)
 73             {
 74                 if(Map[str[2]-'A'][str[0]-'A'] == 1)
 75                 {
 76                     flag2 = true;
 77                     printf("Inconsistency found after %d relations.\n", i);
 78                     continue;
 79                 }
 80                 if(!Map[str[0]-'A'][str[2]-'A'])
 81                 {
 82                     Map[str[0]-'A'][str[2]-'A'] = 1;
 83                     dis[str[2]-'A']++;
 84                 }
 85                 int flag = Topo();
 86                 if(!flag)
 87                 {
 88                     printf("Sorted sequence determined after %d relations: ", i);
 89                     for(int j = 0; j < n; j++)
 90                     {
 91                         printf("%c", Ans[j]+'A');
 92                     }
 93                     printf(".\n");
 94                     flag1 = true;
 95                 }
 96                 else if(flag == 1)
 97                 {
 98                     printf("Inconsistency found after %d relations.\n", i);
 99                     flag2= true;
100                 }
101             }
102         }
103         if(!flag1 &&!flag2)
104         {
105             printf("Sorted sequence cannot be determined.\n");
106         }
107     }
108 }
109 
110 int main(void)
111 {
112     Solve();
113 
114     return 0;
115 }
Sorting It All Out

 

posted @ 2014-01-26 21:19  GLSilence  阅读(281)  评论(0)  编辑  收藏  举报