bzoj1503 Splay 维护名次数，支持删除

题目：http://www.lydsy.com/JudgeOnline/problem.php?id=1503

题解：

维护一颗Splay和一个外部变量，树中每个节点表示一个人，节点权值a + 外部变量delta = 该员工工资。

细节看代码。

注意：一进来工资就低于最低工资的人不能算是“离开公司”的人。

 #include <cstdio>
 #define fprintf(...)
 #define maxn 100100

 struct Splay {
     int key[maxn], pre[maxn], son[maxn][], siz[maxn], ntot, root;
     int trash[maxn], rtot;

     Splay():ntot(),root(),rtot(){}
     void update( int nd ) {
         siz[nd] = siz[son[nd][]] + siz[son[nd][]] + ;
     }
     void rotate( int nd, int d ) {
         int p = pre[nd];
         int s = son[nd][!d];
         int ss = son[s][d];

         if( p ) son[p][ nd==son[p][] ] = s;
         else root = s;
         son[nd][!d] = ss;
         son[s][d] = nd;

         if( ss ) pre[ss] = nd;
         pre[nd] = s;
         pre[s] = p;

         update( nd );
         update( s );
     }
     void splay( int nd, int top= ) {
         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 );
                 }
             }
         }
     }
     int newnode( int k, int p ) {
         int nd;
         if( rtot ) nd = trash[rtot--];
         else nd = ++ntot;
         key[nd] = k;
         pre[nd] = p;
         son[nd][] = son[nd][] = ;
         siz[nd] = ;
         return nd;
     }
     void insert( int k ) {
         fprintf( stderr, "insert(%d)\n", k );
         if( !root ) {
             root = newnode( k,  );
             return;
         }
         int nd = root;
         while( son[nd][ k<key[nd] ] )
             nd = son[nd][ k<key[nd] ];
         son[nd][ k<key[nd] ] = newnode( k, nd );
         update( nd );
         splay( nd,  );
     }
     void erase_subtree( int nd ) {
         fprintf( stderr, "erase_subtree(%d)\n", nd );
         if( !nd ) return;
         erase_subtree( son[nd][] );
         erase_subtree( son[nd][] );
         trash[++rtot] = nd;
     }
     void erase( int k ) {
         fprintf( stderr, "erase(%d)\n", k );
         int nd = root;
         int active = nd;
         while( nd ) {
             if( key[nd]<=k ) {
                 int p = pre[nd];
                 int ls= son[nd][];

                 if( p ) son[p][ nd==son[p][] ] = son[nd][];
                 else root = son[nd][];
                 pre[son[nd][]] = p;

                 pre[nd] = ;
                 son[nd][] = ;

                 erase_subtree( nd );

                 if( p ) update( p );
                 nd = ls;
             } else {
                 active = nd;
                 nd = son[nd][];
             }
         }
         splay(active);
     }
     int nth( int n ) {
         fprintf( stderr, "nth(%d)\n", n );
         int nd = root;
         while() {
             int ls = siz[son[nd][]];
             if( n<=ls ) {
                 nd=son[nd][];
             } else if( n>=ls+ ) {
                 nd=son[nd][];
                 n -= ls+;
             } else
                 break;
         }
         splay( nd );
         return key[nd];
     }
     void print( int nd ) {
         if(!nd) return;
         print( son[nd][] );
         fprintf( stderr, "%d %d %d %d %d\n", nd, pre[nd], son[nd][], son[nd][],
                 key[nd] );
         print( son[nd][] );
     }
 };

 Splay T;
 int n, delta, limit, cnt;

 int main() {
     //freopen( "input", "r", stdin );
     scanf( "%d%d", &n, &limit );
     delta = ;
     cnt = ;
     while(n--) {
         char ch[];
         int k;
         scanf( "%s%d", ch, &k );
         switch(ch[]) {
             case 'I':
                 if( k<limit ) break;
                 cnt++;
                 k -= delta;
                 T.insert( k );
                 break;
             case 'A':
                 delta += k;
                 break;
             case 'S':
                 delta -= k;
                 T.erase( limit-delta- );
                 break;
             case 'F':
                 if( !(<=k && k<=T.siz[T.root]) ) printf( "-1\n" );
                 else printf( "%d\n", T.nth(k)+delta );
                 break;
         }
         fprintf( stderr, "delta=%d\n", delta );
         //T.print( T.root );
         fprintf( stderr, "\n" );
     }
     printf( "%d\n", cnt-T.siz[T.root] );
 }