hicocoder1067 最近公共祖先·二(tarjan算法)

  1 #include <iostream>
  2 #include <string>
  3 #include <map>
  4 #include <vector>
  5 #include <cstring>
  6 
  7 using namespace std;
  8 
  9 #define MAXN 100005
 10 
 11 map<string, int> mp;
 12 string name[2*MAXN];
 13 vector<int> v[2*MAXN];
 14 vector<int> query[2*MAXN];
 15 map<pair<int, int>, int> qid;
 16 string ans[MAXN];
 17 int color[2*MAXN];
 18 bool flag[MAXN];
 19 int n, m, cnt;
 20 vector<int> v1[MAXN];
 21 
 22 struct unionFindSet
 23 {
 24     int st[2*MAXN];
 25     void init()
 26     {
 27         for(int i=0; i<2*MAXN; ++i)   st[i] = i;
 28     }
 29     int findSet(int x)
 30     {
 31         if(x==st[x]) return x;
 32         return st[x] = findSet(st[x]);
 33     }
 34     void unionSet(int x, int y)
 35     {
 36         int sx = findSet(x), sy = findSet(y);
 37         st[sx] = sy;
 38     }
 39 }ufs;
 40 
 41 void init()
 42 {
 43     cnt = 0;
 44     for(int i=0; i<2*MAXN; ++i) v[i].clear();
 45     mp.clear();
 46     for(int i=0; i<2*MAXN; ++i) query[i].clear();
 47     qid.clear();
 48     memset(color, 0x11, sizeof(color));
 49     memset(flag, 0, sizeof(flag));
 50     for(int i=0; i<MAXN; ++i) v1[i].clear();
 51     ufs.init();
 52 }
 53 
 54 void handleRepetition(int x)
 55 {
 56     for(int i=0; i<v1[x].size(); ++i)
 57     {
 58         ans[v1[x][i]] = ans[x];
 59         handleRepetition(v1[x][i]);
 60     }
 61 }
 62 
 63 void solute(int x, int y)
 64 {
 65     if(flag[qid[pair<int, int>(x,y)]]) {}
 66     else if(color[y]==0)
 67     {
 68         ans[qid[pair<int, int>(x,y)]] = name[y];
 69         flag[qid[pair<int, int>(x,y)]] = true;
 70     }
 71     else if(color[y]==1)
 72     {
 73         ans[qid[pair<int, int>(x,y)]] = name[ufs.findSet(y)];
 74         flag[qid[pair<int, int>(x,y)]] = true;
 75     }
 76     if(color[y]>=0) handleRepetition(qid[pair<int, int>(x,y)]);
 77 }
 78 
 79 void tarjan(int x)
 80 {
 81     color[x] = 0;
 82     for(int i=0; i<v[x].size(); ++i)
 83     {
 84         tarjan(v[x][i]);
 85         ufs.unionSet(v[x][i], x);
 86     }
 87     for(int i=0; i<query[x].size(); ++i)    solute(x, query[x][i]);
 88     color[x] = 1;
 89 }
 90 
 91 int main()
 92 {
 93     string name1, name2;
 94     while(cin>>n)
 95     {
 96         init();
 97         while(n--)
 98         {
 99             cin>>name1>>name2;
100             if(mp.find(name1)==mp.end())
101             {
102                 mp[name1] = cnt;
103                 name[cnt++] = name1;
104             }
105             if(mp.find(name2)==mp.end())
106             {
107                 mp[name2] = cnt;
108                 name[cnt++] = name2;
109             }
110             v[mp[name1]].push_back(mp[name2]);
111         }
112         cin>>m;
113         int id = 0;
114         while(m--)
115         {
116             cin>>name1>>name2;
117             query[mp[name1]].push_back(mp[name2]);
118             query[mp[name2]].push_back(mp[name1]);
119             int tmp = -1;
120             if(qid.find(pair<int, int>(mp[name1], mp[name2]))!=qid.end())
121                 tmp = qid[pair<int, int>(mp[name1], mp[name2])];
122             qid[pair<int, int>(mp[name1], mp[name2])] = id++;
123             qid[pair<int, int>(mp[name2], mp[name1])] = id-1;
124             if(tmp!=-1) v1[id-1].push_back(tmp);
125         }
126         tarjan(0);
127         for(int i=0; i<id; ++i) cout<<ans[i]<<endl;
128     }
129 
130     return 0;
131 }