POJ 1986 Distance Queries LCA

  1 #include <cstdio>
  2 #include <cstring>
  3 #include <vector>
  4 #include <algorithm>
  5 #include <iostream>
  6 using namespace std;
  7 const int maxn = 100005;
  8 typedef long long LL;
  9 struct node
 10 {
 11     int x,w;
 12 }ans[maxn];
 13 vector<int>son[maxn];
 14 vector<node>f[maxn];
 15 vector<node>q[maxn];
 16 int d[maxn],vis[maxn],vis1[maxn],fa[maxn],anc[maxn];
 17 //void dfs(int rt)
 18 //{
 19 //    vis[rt] = 1;
 20 //    int len = f[rt].size();
 21 //    for(int i = 0;i<len;++i)
 22 //    {
 23 //        int u = f[rt][i].x;
 24 //        if(vis[u])continue;
 25 //        son[rt].push_back(u);
 26 //        d[u] = d[rt]+f[rt][i].w;
 27 //        dfs(u);
 28 //    }
 29 //}
 30 int findd(int x)
 31 {
 32     int ret = x;
 33     while(ret!=fa[ret])ret=fa[ret];
 34     while(x!=ret)
 35     {
 36         int t = fa[x];
 37         fa[x] = ret;
 38         x = t;
 39     }
 40     return ret;
 41 }
 42 int cnt;
 43 void lca(int rt)
 44 {
 45     vis1[rt] = 1;
 46     int len = f[rt].size();
 47     for(int i = 0;i<len;++i)if(!vis1[f[rt][i].x])
 48     {
 49         d[f[rt][i].x] = d[rt]+f[rt][i].w;
 50         lca(f[rt][i].x);
 51         fa[f[rt][i].x] = rt;
 52     }
 53     vis[rt] = 1;len = q[rt].size();
 54     for(int i = 0;i<len;++i)
 55     {
 56         int u = q[rt][i].w;
 57         if(vis[u]==0)continue;
 58         ans[cnt].x = q[rt][i].x;
 59         ans[cnt++].w = d[rt]+d[u]-2*d[anc[findd(u)]];
 60     }
 61 }
 62 bool cmp(node a,node b)
 63 {
 64     return a.x<b.x;
 65 }
 66 int main()
 67 {
 68     int n,m;
 69     scanf("%d%d",&n,&m);
 70         memset(f,0,sizeof(f));
 71         memset(son,0,sizeof(son));
 72         memset(vis,0,sizeof(vis));
 73         memset(vis1,0,sizeof(vis1));
 74         memset(q,0,sizeof(q));
 75         memset(ans,0,sizeof(ans));
 76         for(int i = 1;i<=n;++i)fa[i] = i,anc[i] = i;
 77         for(int i = 1;i<=m;++i)
 78         {
 79             char s[2];
 80             int x,y,w;scanf("%d%d%d%s",&x,&y,&w,s);
 81             node a,b;
 82             a.x = x;a.w = w;
 83             b.x = y;b.w = w;
 84             f[x].push_back(b);
 85             f[y].push_back(a);
 86         }
 87         cnt = 0;scanf("%d",&m);
 88         for(int i = 1;i<=m;++i)
 89         {
 90             int x,y;scanf("%d%d",&x,&y);
 91             node a,b;
 92             a.x = i;a.w = x;b.x = i;b.w = y;
 93             if(x==y){ans[cnt].x = i;ans[cnt++].w = 0;continue;}
 94             q[x].push_back(b);
 95             q[y].push_back(a);
 96         }
 97 
 98         lca(1);
 99         sort(ans,ans+m,cmp);
100         for(int i = 0;i<m;++i)
101             printf("%d\n",ans[i].w);
102     return 0;
103 }