hdu 2460 Network (双连通分支+暴力LCA)

  1 /**************************************************
  2  * Author     : xiaohao Z
  3  * Blog     : http://www.cnblogs.com/shu-xiaohao/
  4  * Last modified : 2014-09-01 15:25
  5  * Filename     : hdu_2460.cpp
  6  * Description     : 
  7  * ************************************************/
  8 #pragma comment(linker, "/STACK:1024000000,1024000000")
  9 #include <iostream>
 10 #include <cstdio>
 11 #include <cstring>
 12 #include <cstdlib>
 13 #include <string>
 14 #include <cmath>
 15 #include <algorithm>
 16 #include <queue>
 17 #include <stack>
 18 #include <vector>
 19 #include <set>
 20 #include <map>
 21 #define MP(a, b) make_pair(a, b)
 22 #define PB(a) push_back(a)
 23 
 24 using namespace std;
 25 typedef long long ll;
 26 typedef pair<int, int> pii;
 27 typedef pair<unsigned int,unsigned int> puu;
 28 typedef pair<int, double> pid;
 29 typedef pair<ll, int> pli;
 30 typedef pair<int, ll> pil;
 31 
 32 const int INF = 0x3f3f3f3f;
 33 const double eps = 1E-6;
 34 const int LEN = 100010;
 35 vector<int> Map[LEN], tMap[LEN];
 36 stack<int> s;
 37 int n, m, dclock, low[LEN], dfn[LEN], block, blong[LEN];
 38 int dep[LEN], parent[LEN], is[LEN];
 39 
 40 void init()
 41 {
 42     memset(dfn, -1, sizeof dfn);
 43     memset(is, 0, sizeof is);
 44     memset(parent, 0, sizeof parent);
 45     dclock = is[1] = 1; block = 0;
 46     while(!s.empty())s.pop();
 47     for(int i=0; i<LEN; i++) Map[i].clear();
 48 }
 49 
 50 void dfs(int u, int fa){
 51     int v, flag = 0;
 52     dfn[u] = low[u] = dclock++;
 53     s.push(u);
 54     for(int i=0; i<Map[u].size(); i++){
 55         v = Map[u][i];
 56         if(v==fa && !flag){flag = 1;continue;}
 57         if(dfn[v]<0){
 58             dfs(v, u);
 59             low[u] = min(low[u], low[v]);
 60         }else if(low[u]>low[v]) low[u] = min(low[u], dfn[v]);
 61     }
 62     if(low[u] == dfn[u]){
 63         block ++;
 64         do{
 65             v = s.top(); s.pop();
 66             blong[v] = block;
 67         }while(v!=u);
 68     }
 69 }
 70 
 71 void DFS(int v, int fa, int d){
 72     dep[v] = d;
 73     parent[v] = fa;
 74     for(int i=0; i<tMap[v].size(); i++){
 75         int x = tMap[v][i];
 76         if(x != fa)    DFS(x, v, d+1);
 77     }
 78 }
 79 
 80 void build(){
 81     int a, b;
 82     map<pii, int> mp; mp.clear();
 83     for(int i=0; i<LEN; i++) tMap[i].clear();
 84     for(int i=0; i<n; i++)
 85         for(int j=0; j<Map[i].size(); j++){
 86             int x = Map[i][j];
 87             if(blong[i] == blong[x]) continue;
 88             a = blong[i], b = blong[x];
 89             if(mp.count(MP(a, b))) continue;
 90             mp[MP(a, b)] = mp[MP(b, a)] = 1;
 91             tMap[a].PB(b); tMap[b].PB(a);
 92         }
 93     DFS(1, 0, 0);
 94 }
 95 
 96 void _(int val) {cout << "\"" << val << endl;}
 97 
 98 
 99 void lca(int a, int b){
100     if(dep[a] < dep[b]) swap(a, b);
101     int tmp = dep[a] - dep[b];
102     for(int i=0; i<tmp; i++) {
103         if(!is[a]) {is[a] = 1;block --;}
104         a = parent[a];
105     }
106     while(a != b) {
107         if(!is[a]) {is[a] = 1; block --;}
108         if(!is[b]) {is[b] = 1; block --;}
109         a = parent[a], b = parent[b];
110     }
111 }
112 
113 int main()
114 {
115 //    freopen("in.txt", "r", stdin);
116 
117     int a, b, q, kase = 1;
118     while(scanf("%d%d", &n, &m) != EOF){
119         if(!n && !m) break;
120         init();
121         for(int i=0; i<m; i++){
122             scanf("%d%d", &a, &b);
123             a--, b--;
124             Map[a].PB(b); Map[b].PB(a);
125         }
126         dfs(0, -1);
127         build();
128         scanf("%d", &q);
129         printf("Case %d:\n", kase ++);
130         for(int i=0; i<q; i++){
131             scanf("%d%d", &a, &b);
132             a--; b--;
133             if(blong[a] != blong[b]) lca(blong[a], blong[b]);
134             printf("%d\n", block - 1);
135         }
136         puts("");
137     }
138     return 0;
139 }