spoj4155 OTOCI LCT

动态树，支持加边，修改点权，查询链的点权和。

 #include <cstdio>
 #include <iostream>
 #define maxn 30010
 using namespace std;

 namespace L {
     int pnt[maxn], pre[maxn], son[maxn][], val[maxn], sum[maxn], rtg[maxn];

     void update( int nd ) {
         sum[nd] = val[nd] + sum[son[nd][]] + sum[son[nd][]];
     }
     void rotate( int nd, int d ) {
         int p = pre[nd];
         int s = son[nd][!d];
         int ss = son[s][d];
         son[nd][!d] = ss;
         son[s][d] = nd;
         if( p ) son[p][ nd==son[p][] ] = s;
         else pnt[s] = pnt[nd];
         pre[nd] = s;
         pre[s] = p;
         pre[ss] = nd;
         update( nd );
         update( s );
     }
     void pushdown( int nd ) {
         if( rtg[nd] ) {
             int &ls = son[nd][], &rs = son[nd][];
             swap(ls,rs);
             rtg[ls] ^= ;
             rtg[rs] ^= ;
             rtg[nd] = ;
         }
     }
     void big_push( int nd ) {
         if( pre[nd] ) big_push(pre[nd]);
         pushdown(nd);
     }
     void splay( int nd, int top= ) {
         big_push(nd);
         while( pre[nd]!=top ) {
             int p = pre[nd];
             int nl = nd==son[p][];
             if( pre[p]==top ) {
                 rotate( p, nl );
             } else {
                 int pp = pre[p];
                 int pl = p==son[pp][];
                 if( nl==pl ) {
                     rotate( pp, pl );
                     rotate( p, nl );
                 } else {
                     rotate( p, nl );
                     rotate( pp, pl );
                 }
             }
         }
     }
     void access( int nd ) {
         int u = nd;
         int v = ;
         while( u ) {
             splay( u );
             int s = son[u][];
             pre[s] = ;
             pnt[s] = u;
             pre[v] = u;
             son[u][] = v;
             update( u );
             v = u;
             u = pnt[u];
         }
         splay(nd);
     }
     void makeroot( int nd ) {
         access(nd);
         rtg[nd] ^= ;
     }
     int findroot( int nd ) {
         while( pre[nd] ) nd=pre[nd];
         while( pnt[nd] ) {
             nd = pnt[nd];
             while( pre[nd] ) nd=pre[nd];
         }
         return nd;
     }
     bool sameroot( int u, int v ) {
         return findroot(u)==findroot(v);
     }
     void link( int u, int v ) {
         makeroot(u);
         makeroot(v);
         pnt[u] = v;
     }
     void up_val( int nd, int v ) {
         splay( nd );
         val[nd] = v;
         update( nd );
     }
     int qu_sum( int u, int v ) {
         makeroot(u);
         access(v);
         return val[v]+sum[son[v][]];
     }
 };

 int n, q;

 int main() {
     scanf( "%d", &n );
     for( int i=, w; i<=n; i++ ) {
         scanf( "%d", &w );
         L::up_val( i, w );
     }
     scanf( "%d", &q );
     while( q-- ) {
         char ch[];
         int u, v, w;
         scanf( "%s", ch );
         if( ch[]=='b' ) {
             scanf( "%d%d", &u, &v );
             if( L::sameroot(u,v) ) printf( "no\n" );
             else {
                 printf( "yes\n" );
                 L::link(u,v);
             }
         } else if( ch[]=='p' ) {
             scanf( "%d%d", &u, &w );
             L::up_val( u, w );
         } else {
             scanf( "%d%d", &u, &v );
             if( L::sameroot(u,v) )
                 printf( "%d\n", L::qu_sum(u,v) );
             else
                 printf( "impossible\n" );
         }
     }
 }