uva-315.network(连通图的割点)

本题大意:求一个无向图额割点的个数.

本题思路:建图之后打一遍模板.

 1 /*************************************************************************
 2     > File Name: uva-315.network.cpp
 3     > Author: CruelKing
 4     > Mail: 2016586625@qq.com 
 5     > Created Time: 2019年09月06日 星期五 17时15分07秒
 6     本题思路:就是求图中有多少个割点
 7  ************************************************************************/
 8 
 9 #include <cstdio>
10 #include <iostream>
11 #include <sstream>
12 #include <cstring>
13 #include <string>
14 using namespace std;
15 
16 const int maxn = 100 + 5, maxm = maxn * maxn + 5;
17 int tot, head[maxn];
18 
19 struct Edge {
20     int to, next;
21 } edge[maxm];
22 
23 void init() {
24     memset(head, -1, sizeof head);
25     tot = 0;
26 }
27 
28 void addedge(int u, int v) {
29     edge[tot] = (Edge) {v, head[u]}; head[u] = tot ++;
30     edge[tot] = (Edge) {u, head[v]}; head[v] = tot ++;
31 }    
32 
33 int n;
34 string str;
35 
36 int dfn[maxn], low[maxn], stack[maxn];
37 bool cut[maxn], instack[maxn];
38 int Index, top, cut_num;
39 
40 void tarjan(int u, int pre) {
41     dfn[u] = low[u] = ++ Index;
42     instack[u] = true;
43     stack[top ++] = u;
44     int son = 0;
45     for(int i = head[u]; ~i; i = edge[i].next) {
46         int v = edge[i].to;
47         if(!dfn[v]) {
48             son ++;
49             tarjan(v, u);
50             if(low[u] > low[v]) low[u] = low[v];
51             if(pre != u && low[v] >= dfn[u]) {
52                 cut[u] = true;
53             }
54         } else if(low[u] > dfn[v]) low[u] = dfn[v];
55     }
56     if(u == pre && son > 1) {
57         cut[u] = true;
58     }
59     instack[u] = false;
60     top --;
61 }
62 
63 void solve() {
64     memset(dfn, 0, sizeof dfn);
65     memset(low, 0, sizeof low);
66     memset(cut, false, sizeof cut);
67     Index = top = cut_num = 0;
68     for(int i = 1; i <= n; i ++) {
69         if(!dfn[i]) tarjan(i, i);
70     }
71     for(int i = 1; i <= n; i ++) if(cut[i]) cut_num ++;
72     printf("%d\n", cut_num);
73 }
74 
75 int main() {
76     int u, v;
77     while(~scanf("%d", &n) && n) {
78         init();
79         while(scanf("%d", &u)) {
80             if(u == 0) break;
81             getline(cin, str);
82             stringstream ss;
83             ss << str;
84             while(ss >> v) addedge(u, v);
85         }
86         solve();
87     }
88     return 0;
89 }

 

posted @ 2019-09-06 17:43  Cruel_King  阅读(185)  评论(0)  编辑  收藏  举报