targan算法。
1 # include <cstdio> 2 # include <cstring> 3 4 # define N (1000 + 5) 5 6 int n, son, tmpdfn; 7 int low[N], dfn[N], subnets[N]; 8 char g[N][N]; 9 10 int Min(int x, int y) 11 { 12 return x<y ? x:y; 13 } 14 15 void tarjan(int u, int r) 16 { 17 dfn[u] = low[u] = ++tmpdfn; 18 for (int v = 1; v <= n; ++v) if (g[u][v]) 19 { 20 if (!dfn[v]) 21 { 22 //dfn[v] = low[v] = ++tmpdfn; // 时间戳打在这里就忽略了节点r，原图可能是不联通的（这道题是联通的） 23 tarjan(v, r); 24 low[u] = Min(low[u], low[v]); 25 if (low[v] >= dfn[u]) 26 { 27 if (u != r) ++subnets[u]; 28 else ++son; 29 } 30 } 31 else 32 low[u] = Min(low[u], dfn[v]); 33 } 34 } 35 36 void init(void) 37 { 38 tmpdfn = 0; 39 memset(low+1, 0, sizeof(int)*n); 40 memset(dfn+1, 0, sizeof(int)*n); 41 memset(subnets+1, 0, sizeof(int)*n); 42 } 43 44 void solve(void) 45 { 46 bool find = false; 47 for (int i = 1; i <= n; ++i) if (!dfn[i]) 48 { 49 son = 0; 50 tarjan(i, i); 51 if (son > 1) subnets[i] = son - 1; 52 } 53 for (int i = 1; i <= n; ++i) 54 { 55 if (subnets[i]) 56 { 57 find = true; 58 printf("\n SPF node %d leaves %d subnets", i, subnets[i]+1); 59 } 60 } 61 if (find == false) 62 printf("\n No SPF nodes"); 63 } 64 65 int read_graph(void) 66 { 67 n = 0; 68 memset(g, 0, sizeof(g)); 69 int x, y; 70 scanf("%d", &x); 71 if (x == 0) return 0; 72 do 73 { 74 scanf("%d", &y); 75 g[x][y] = g[y][x] = 1; 76 if (x > n) n = x; 77 if (y > n) n = y; 78 }while (scanf("%d", &x), x); 79 return 1; 80 } 81 82 int main() 83 { 84 int icase = 0; 85 while (read_graph()) 86 { 87 if (icase != 0) printf("\n\n"); 88 printf("Network #%d", ++icase); 89 init(); 90 solve(); 91 } 92 }
注意n=1的情况。