Poj_1523 SPF (Tarjan cut point)

Question: Find the cut point and find the remaining number of connected blocks after the cut point is deleted.

Slag code:

View code

 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 }