uva 315 (poj 1144 求割点)

题意：给你一张无向图，求割点的个数。

思路：输入稍微处理一下接着直接套模版。

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cstdlib>
 5 #include <cmath>
 6 #include <algorithm>
 7 #include <queue>
 8 #include <stack>
 9 #include <vector>
10 #include <set>
11 #include <map>
12 #define MP(a, b) make_pair(a, b)
13 #define PB(a) push_back(a)
14 
15 using namespace std;
16 
17 typedef long long ll;
18 typedef pair<int, int> pii;
19 typedef pair<unsigned int, unsigned int> puu;
20 typedef pair<int, ll> pil;
21 typedef pair<int,double> pid;
22 
23 const int INF = 0x3f3f3f3f;
24 const double eps = 1e-6;
25 const int LEN = 101;
26 int cnt, n, cut[LEN], low[LEN], dfn[LEN], vis[LEN];
27 vector<int> Map[LEN];
28 
29 //割点模版初始化vis[] cut[]置0
30 //求割点若有重边需要判重
31 void dfs(int u, int fa){
32     int v, i, son = 0;
33     vis[u] = 1;
34     dfn[u] = low[u] = cnt ++;
35     for(i = 0; i < Map[u].size(); i ++){
36         v = Map[u][i];
37         if(vis[v] == 1 && v != fa)
38             low[u] = min(low[u], dfn[v]);
39         if(vis[v] == 0){
40             dfs(v, u);
41             son ++;
42             low[u] = min(low[u], low[v]);
43             if((fa < 0 && son > 1) || (fa > 0 && low[v] >= dfn[u]))
44                 cut[u] = true;
45             //if(low[v] > dfn[u]){
46             //   bridge[nbri][0] = u; bridge[nbri++][1] = v;   //边(i,j)是桥。
47             //}
48         }
49     }
50     vis[u] = 2;
51 }
52 
53 int main()
54 {
55 //    freopen("in.txt", "r", stdin);
56 
57     int from, to;
58     while(scanf("%d", &n)!=EOF && n){
59         for(int i=0; i<LEN; i++)Map[i].clear();
60         while(scanf("%d", &from) && from){
61             while(getchar()!='\n'){
62                 scanf("%d", &to);
63                 Map[from].PB(to);
64                 Map[to].PB(from);
65             }
66         }
67         cnt = 0;
68         memset(vis, 0, sizeof vis);
69         memset(cut, 0, sizeof cut);
70         dfs(1,-1);
71         int ans = 0;
72         for(int i=1; i<=n; i++)ans+=cut[i];
73         printf("%d\n", ans);
74     }
75     return 0;
76 }
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posted @ 2014-01-15 15:33  张小豪  阅读(195)  评论(0)  编辑  收藏  举报