倍增求LCA的模板

/*2^17=131072;2^18=262144;*/const int POW = 18;void dfs(int u,int fa){d[u]=d[fa]+1;    p[u][0]=fa;for(int i=1;i<POW;i++) p[u][i]=p[p[u][i-1]][i-1];int sz=edge[u].size();for(int i=0;i<sz;i++){int v=edge[u][i];if(v==fa) continue;dfs(v,u);}}int lca( int a, int b ){if( d[a] > d[b] ) a ^= b, b ^= a, a ^= b;if( d[a] < d[b] ){int del = d[b] - d[a];for( int i = 0; i < POW; i++ ) if(del&(1<<i)) b=p[b][i];}if( a != b ){for( int i = POW-1; i >= 0; i-- ) if( p[a][i] != p[b][i] )      a = p[a][i] , b = p[b][i];a = p[a][0], b = p[b][0];}return a;}

转自http://blog.csdn.net/haha593572013/article/details/7796497