tyvj P1039 忠诚2——线段树实现动态查询区间极值

    本来想给出一个链接，tyvjp1039忠诚2，大家自己找一下吧。这个问题很明显是区间极值问题，而且是动态的，这样就不能用RMQ了。线段树是一个比较好的选择。而且我发现一个问题，从前以为线段树之类的东西代码比较死，基本上都一样，其实我错了，越是高级的数据结构写法往往越活，变通性很强。只可惜此生无缘noi啦，这能自己虐一些简单的题目找找爽啦！悲剧呀！

 

  
    

   
      1 
   
     type 

   
      2 
   
      ji
   
     =^
   
     rec;

   
      3 
   
      rec
   
     =
   
     record

   
      4 
   
      l,r,min:longint;

   
      5 
   
      lson,rson:ji;

   
      6 
   
     end;

   
      7 
   
     

   
      8 
   
     var

   
      9 
   
      a:ji;

   
     10 
   
      b:array[
   
     0
   
     ..
   
     100000
   
     ] of longint;

   
     11 
   
      i,j,x,y,m,n:longint;

   
     12 
   
     

   
     13 
   
     function minn(x,y:longint):longint;

   
     14 
   
     begin

   
     15 
   
      
   
     if
   
      x
   
     <
   
     y then exit(x);

   
     16 
   
      exit(y);

   
     17 
   
     end;

   
     18 
   
     

   
     19 
   
     procedure build(var a:ji; l,r:longint);

   
     20 
   
     var

   
     21 
   
      mid:longint;

   
     22 
   
     begin

   
     23 
   
      
   
     new
   
     (a); 

   
     24 
   
      a
   
     ^
   
     .l:
   
     =
   
     l;

   
     25 
   
      a
   
     ^
   
     .r:
   
     =
   
     r;

   
     26 
   
      mid:
   
     =
   
     (l
   
     +
   
     r)
   
     >>
   
     1
   
     ;

   
     27 
   
      
   
     if
   
      l
   
     =
   
     r then 

   
     28 
   
      begin

   
     29 
   
      a
   
     ^
   
     .min:
   
     =
   
     b[l];

   
     30 
   
      exit;

   
     31 
   
      end;

   
     32 
   
      build(a
   
     ^
   
     .lson,l,mid);

   
     33 
   
      build(a
   
     ^
   
     .rson,mid
   
     +
   
     1
   
     ,r);

   
     34 
   
      a
   
     ^
   
     .min:
   
     =
   
     minn(a
   
     ^
   
     .lson
   
     ^
   
     .min,a
   
     ^
   
     .rson
   
     ^
   
     .min);

   
     35 
   
     end;

   
     36 
   
     

   
     37 
   
     function find(a:ji; l,r:longint):longint;

   
     38 
   
     var

   
     39 
   
      mid,k:longint;

   
     40 
   
     begin

   
     41 
   
      
   
     if
   
      (l
   
     <=
   
     a
   
     ^
   
     .l)and(r
   
     >=
   
     a
   
     ^
   
     .r) then exit(a
   
     ^
   
     .min);

   
     42 
   
      mid:
   
     =
   
     (a
   
     ^
   
     .l
   
     +
   
     a
   
     ^
   
     .r)
   
     >>
   
     1
   
     ; k:
   
     =
   
     maxlongint;

   
     43 
   
      
   
     if
   
      mid
   
     >=
   
     l then k:
   
     =
   
     minn(k,find(a
   
     ^
   
     .lson,l,r));

   
     44 
   
      
   
     if
   
      mid
   
     <
   
     r then k:
   
     =
   
     minn(k,find(a
   
     ^
   
     .rson,l,r));

   
     45 
   
      exit(k);

   
     46 
   
     end;

   
     47 
   
     

   
     48 
   
     procedure change(var a:ji; x,y:longint);

   
     49 
   
     var

   
     50 
   
      mid:longint;

   
     51 
   
     begin

   
     52 
   
      
   
     if
   
      (x
   
     =
   
     a
   
     ^
   
     .l)and(x
   
     =
   
     a
   
     ^
   
     .r) then 

   
     53 
   
      begin

   
     54 
   
      a
   
     ^
   
     .min:
   
     =
   
     y;

   
     55 
   
      exit;

   
     56 
   
      end;

   
     57 
   
      mid:
   
     =
   
     (a
   
     ^
   
     .l
   
     +
   
     a
   
     ^
   
     .r)
   
     >>
   
     1
   
     ;

   
     58 
   
      
   
     if
   
      mid
   
     >=
   
     x then change(a
   
     ^
   
     .lson,x,y);

   
     59 
   
      
   
     if
   
      mid
   
     <
   
     x then change(a
   
     ^
   
     .rson,x,y);

   
     60 
   
      a
   
     ^
   
     .min:
   
     =
   
     minn(a
   
     ^
   
     .lson
   
     ^
   
     .min,a
   
     ^
   
     .rson
   
     ^
   
     .min);

   
     61 
   
     end;

   
     62 
   
     

   
     63 
   
     begin

   
     64 
   
      readln(n,m);

   
     65 
   
      
   
     for
   
      i:
   
     =
   
     1
   
      to n 
   
     do
   
      read(b[i]);

   
     66 
   
      build(a,
   
     1
   
     ,n);

   
     67 
   
      
   
     for
   
      i:
   
     =
   
     1
   
      to m 
   
     do
   
     

   
     68 
   
      begin

   
     69 
   
      readln(j,x,y);

   
     70 
   
      
   
     if
   
      j
   
     =
   
     1
   
      then write(find(a,x,y),
   
     '
   
      
   
     '
   
     )

   
     71 
   
      
   
     else
   
      change(a,x,y);

   
     72 
   
      end;

   
     73 
   
     end.