Uva796 Critical Links

用tarjan缩点 
然后用dfn[u] < low[v]缩点并且保存起来 
在sort一遍输出

  1 #include<stdio.h>
  2 #include<string.h>
  3 #include<algorithm>
  4 
  5 using namespace std;
  6 
  7 const int maxn = 10000;
  8 
  9 struct Node {
 10     int u;
 11     int v;
 12     int next;
 13 };
 14 struct Edge{
 15     int u;
 16     int v;
 17 }; 
 18 Edge edge[maxn];
 19 Node node[maxn * 10];
 20 int head[maxn];
 21 int dfn[maxn];
 22 int low[maxn];
 23 int fath[maxn];
 24 bool vis[maxn];
 25 bool maps[maxn][maxn];
 26 int n, tol, cnt;
 27 
 28 void init() {
 29     cnt = tol= 0;
 30     memset(dfn, 0, sizeof(dfn));
 31     memset(low, 0, sizeof(low));
 32     memset(maps, 0, sizeof(maps));
 33     memset(fath, 0, sizeof(fath));
 34     memset(head, -1, sizeof(head));
 35     memset(vis, false, sizeof(vis));
 36 }
 37 
 38 void addnode(int u, int v) {
 39     node[tol].u = u;
 40     node[tol].v = v;
 41     node[tol].next = head[u];
 42     head[u] = tol++;
 43 }
 44 
 45 void dfs(int u, int fa){
 46     fath[u] = fa;
 47     low[u] = dfn[u] = ++cnt;
 48     vis[u] = true;
 49     for(int i=head[u]; i!=-1; i=node[i].next) {
 50         int v = node[i].v;
 51         if(!dfn[v]) {
 52             dfs(v, u);
 53             low[u] = min(low[u], low[v]);
 54         } else if(v != fa) {
 55             low[u] = min(low[u], dfn[v]);
 56         }
 57     }
 58 }
 59 
 60 void tarjan() {
 61     for(int u=0; u<n; u++) {
 62         if(!dfn[u]) {
 63             dfs(u, u);
 64         }
 65     }
 66 }
 67 
 68 bool cmp(Edge a, Edge b) {
 69     if(a.u == b.u)
 70         return a.v < b.v;
 71     else
 72         return a.u < b.u;
 73 }
 74 
 75 void solve() {
 76     tol = 0;
 77     for(int u=0; u<n; u++) {
 78         int v = fath[u];
 79         if(low[u] > dfn[v] && v != u) {
 80             edge[tol].u = u;
 81             edge[tol].v = v;
 82             if(edge[tol].u > edge[tol].v)
 83                 swap(edge[tol].u, edge[tol].v);
 84             tol++;
 85         }
 86     }
 87     sort(edge, edge+tol, cmp);  
 88     printf("%d critical links\n", tol); 
 89     for(int i=0; i<tol; i++) {
 90         printf("%d - %d\n", edge[i].u, edge[i].v);
 91     }
 92     printf("\n");
 93 }
 94 
 95 int main() {
 96     while(scanf("%d", &n) != EOF) {
 97         init();
 98         if(n == 0) {
 99             printf("0 critical links\n\n");
100             continue;
101         }
102         for(int i=1; i<=n; i++) {
103             int u;
104             int num;
105             scanf("%d (%d)", &u, &num);
106             for(int j=1; j<=num; j++) {
107                 int v;
108                 scanf("%d", &v);
109                 maps[u][v] = maps[v][u] = 1; 
110             }
111         }
112         for(int i=0; i<n; i++) {
113             for(int j=i+1; j<n; j++) {
114                 if(maps[i][j]) {
115                     addnode(i, j);
116                     addnode(j, i);
117                 }
118             }
119         }
120         tarjan();
121         solve();
122     }
123     return 0;
124 }
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posted @ 2018-06-07 00:55  Jiaaaaaaaqi  阅读(132)  评论(0)    收藏  举报