输入：顶点个数n，边数m，然后是m行，表示每条边的起点和终点u, v 表示从顶点u到顶点v的一条有向边。输入0 0 表示结束。
输出：如果不存在有向环，则输出一个拓扑有序序列；否则，输出“Netword has a cycle!”
1 #include <iostream> 2 #include <cstdio> 3 #include <cstdlib> 4 #include <cstring> 5 #include <cctype> 6 #include <stack> 7 #include <queue> 8 #include <map> 9 #include <set> 10 #include <vector> 11 #include <cmath> 12 #include <algorithm> 13 #define lson l, m, rt<<1 14 #define rson m+1, r, rt<<1|1 15 using namespace std; 16 typedef long long int LL; 17 const int MAXN = 0x3f3f3f3f; 18 const int MIN = -0x3f3f3f3f; 19 const double eps = 1e-9; 20 const int dir[8][2] = {{0,1},{1,0},{0,-1},{-1,0},{-1,1}, 21 {1,1},{1,-1},{-1,-1}}; 22 int n, m, Count[100], i, j, top, out[100]; 23 struct ArcNode{ 24 int to; struct ArcNode *next; 25 }; 26 ArcNode *List[100]; 27 void topsort() 28 { 29 ArcNode *temp; top = -1; int k, len = 0; bool flag = true; 30 for (i = 0; i < n; ++i) { 31 if (Count[i] == 0) { 32 Count[i] = top; top = i; 33 } 34 } 35 for (i = 0; i < n; ++i) { 36 k = top; if (k == -1) { flag = false; break; } 37 top = Count[k]; temp = List[k]; out[len++] = k + 1; 38 while (temp != NULL) { 39 Count[temp->to]--; 40 if (Count[temp->to] == 0) { 41 Count[temp->to] = top; top = temp->to; 42 } temp = temp->next; 43 } 44 } 45 if (flag) { 46 for (i = 0; i < len; ++i) { 47 if (!i) printf("%d", out[i]); else printf(" %d", out[i]); 48 } printf("\n"); 49 } else printf("Network has a cycle!\n"); 50 for (i = 0; i < n; ++i) { 51 temp = List[i]; 52 while (temp) { 53 List[i] = temp->next; delete temp; temp = List[i]; 54 } 55 } 56 } 57 int main(void){ 58 #ifndef ONLINE_JUDGE 59 freopen("topsort.in", "r", stdin); 60 #endif 61 while (~scanf("%d%d", &n, &m)){ 62 if (m + n == 0) break; 63 int u, v; ArcNode *temp; 64 memset(Count, 0, sizeof(Count)); 65 memset(List, 0, sizeof(List)); 66 memset(out, 0, sizeof(out)); 67 for (i = 0; i < m; ++i){ 68 scanf("%d%d", &u, &v); u--; v--; 69 temp = new ArcNode; temp->next = NULL; temp->to = v; 70 temp->next = List[u]; List[u] = temp; Count[v]++; 71 } 72 topsort(); 73 } 74 75 return 0; 76 }
用数组实现的链式栈 ，好神奇……
