POJ_1523 SPF (Tarjan 求割点)
题意：求割点，并求出割点删掉后剩下的连通块数
渣代码：
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1 #include <iostream>
2 #include <cstring>
3 #include <cstdio>
4
5 using namespace std;
6
7 const int N = 1005;
8 const int M = 100000;
9 const int inf = ~0u>>2;
10
11 struct node {
12 int to;
13 int next;
14 } g[M];
15
16 int head[N], cut[N];
17 int dfn[N], low[N];
18 int t, ind, rot, r_son;
19 bool vis[N];
20
21 void init() {
22 memset(head, 0, sizeof(head));
23 memset(cut, 0, sizeof(cut));
24 memset(dfn, 0, sizeof(dfn));
25 memset(low, 0, sizeof(low));
26 memset(vis, 0, sizeof(vis));
27 t = 1; r_son = ind = 0;
28 }
29
30 void add(int u, int v) {
31 g[t].to = v; g[t].next = head[u]; head[u] = t++;
32
33 }
34
35 void tarjan(int u) {
36 int v, i;
37 dfn[u] = low[u] = ++ind;
38 for(i = head[u]; i; i = g[i].next) {
39 v = g[i].to;
40 if(!dfn[v]) {
41 tarjan(v);
42 //printf("%d %d\n", u, v);
43 if(u == rot) r_son++;
44 else {
45 low[u] = min(low[u], low[v]);
46 if(low[v] >= dfn[u]) cut[u]++;
47 }
48 }
49 else {
50 low[u] = min(low[u], dfn[v]);
51 }
52 }
53 }
54
55 int main() {
56 //freopen("data.in", "r", stdin);
57
58 int u, v, cas = 0;
59 int MIN, MAX, i;
60 bool f;
61 while(scanf("%d", &u), u) {
62 init();
63 MIN = inf; MAX = -1;
64 scanf("%d", &v);
65 add(u, v); add(v, u);
66
67 MIN = min(MIN, min(u, v));
68 MAX = max(MAX, max(u, v));
69
70 while(scanf("%d", &u), u) {
71 scanf("%d", &v);
72 add(u, v); add(v, u);
73
74 MIN = min(MIN, min(u, v));
75 MAX = max(MAX, max(u, v));
76 }
77 rot = MIN;
78 tarjan(rot);
79 cut[rot] = r_son - 1;
80 printf("Network #%d\n", ++cas);
81
82 for(f = false, i = MIN; i <= MAX; i++) {
83 if(cut[i]) {
84 f = true;
85 printf(" SPF node %d leaves %d subnets\n", i, cut[i] + 1);
86 }
87 }
88 if(!f) printf(" No SPF nodes\n");
89 cout << endl;
90 }
91 return 0;
92 }
