poj 1094

拓扑排序，对有环、多种排序、唯一排序分情况即可

  1 #include <iostream>
  2 #include <string>
  3 #include <vector>
  4 #include <cstdlib>
  5 #include <cmath>
  6 #include <map>
  7 #include <algorithm>
  8 #include <list>
  9 #include <ctime>
 10 #include <set>
 11 #include <cstring>
 12 #include <queue>
 13 #include <cstdio>
 14 #include <stack>
 15 using namespace std;
 16 /*==================================================*\
 17   |  拓扑排序
 18  | INIT:edge[][] 置为图的邻接矩阵;count[0…i…n-1]: 顶点i 的入度.
 19  | 和TopoOrder实现的原理是一样的，只是没有用count。
 20  \*==================================================*/
 21 const int V = 30;
 22 int countk[V];
 23 int edge[V][V];
 24 int topres[V];
 25 int n;
 26 #define CLR(arr, what) memset(arr, what, sizeof(arr))
 27 /*
 28  1:有环
 29  0:ok
 30  -1:不确定
 31  */
 32 int TopOrder_easy() {
 33     int i;
 34     stack<int> sh;
 35     int ct = 0;
 36     CLR(countk, 0);
 37     for (i = 0; i < n; ++i) {
 38         for (int j = 0; j < n; j++) {
 39             if (1 == edge[i][j]) {
 40                 countk[j] += 1;
 41             }
 42         }
 43     }
 44     for (i = 0; i < n; ++i)
 45         if (countk[i] == 0) { //  下标模拟堆栈
 46             sh.push(i);
 47         }
 48 
 49     for (i = 0; i < n; ++i) {
 50         if (sh.empty()) {
 51             return 1;
 52         } else {
 53             if (sh.size() > 1)
 54                 ct = 1;
 55             int j = sh.top();
 56             sh.pop();
 57             topres[i] = j;
 58             for (int k = 0; k < n; ++k)
 59                 if (edge[j][k] && (--countk[k]) == 0) {
 60                     sh.push(k);
 61                 }
 62         }
 63     }
 64     if (ct > 0)
 65         return -1;
 66     return 0;
 67 }
 68 void addnode(int u, int v) {
 69     edge[u][v] = 1;
 70 }
 71 void printres() {
 72     char t;
 73     for (int i = 0; i < n; i++) {
 74         t = topres[i] + 'A';
 75         cout << t;
 76     }
 77 }
 78 void eat_useless(int numt){
 79     string t;
 80     for(int i=0;i<numt;i++){
 81         cin>>t;
 82     }
 83 }
 84 int main() {
 85     int num, judge;
 86     char t[4];
 87     cin >> n >> num;
 88     while (n || num) {
 89         CLR(edge, 0);
 90         int a;
 91         for (a = 0; a < num; a++) {
 92             scanf("%s",t);
 93             int u = t[0] - 'A';
 94             int v = t[2] - 'A';
 95             addnode(u, v);
 96             judge = TopOrder_easy();
 97             if (-1 == judge && (num - 1) == a) {
 98                 cout << "Sorted sequence cannot be determined.\n";
 99             } else if (0 == judge) {
100                 cout << "Sorted sequence determined after " << a + 1
101                         << " relations: ";
102                 printres();
103                 cout << ".\n";
104                 eat_useless(num-a-1);
105                 break;
106             } else if (1 == judge) {
107                 cout << "Inconsistency found after " << a + 1
108                         << " relations.\n";
109                 eat_useless(num-a-1);
110                 break;
111             }
112         }
113         if (0 == num) {
114             cout << "Sorted sequence cannot be determined.\n";
115         }
116         scanf("%d%d", &n, &num);
117     }
118     return 0;
119 }

from kakamilan

 

posted on 2013-05-16 16:17  kakamilan  阅读(124)  评论(0)  编辑  收藏  举报

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