POJ1990 MooFest——树状数组——Pku1990

维护两个树状数组，一个记录这个坐标所控制的范围内的奶牛个数，另外一个记录这个坐标所控制范围内的奶牛坐标之和。

program poj1990;//by_poetshy
const 
    maxn=20000;
var
    i,n                            :longint;
    p,m,ans                        :int64;
    v,x,a,h                        :array[1..maxn]of int64;
    
procedure qsort(l,r:longint);
var i,j,k,temp:longint;
begin
    i:=l;j:=r;k:=v[(i+j)>>1];
    repeat
        while v[i]<k do inc(i);
        while v[j]>k do dec(j);
        if i<=j then 
            begin
                temp:=x[i];x[i]:=x[j];x[j]:=temp;
                temp:=v[i];v[i]:=v[j];v[j]:=temp;
                inc(i);dec(j);
            end;
    until i>j;
    if i<r then qsort(i,r);
    if l<j then qsort(l,j);
end;
    
function count(i:longint):int64;
begin
    count:=0;
    while i>0 do 
        begin
            inc(count,a[i]);
            dec(i,(i)and(-i));
        end;
end;
    
function counth(i:longint):int64;
begin
    counth:=0;
    while i>0 do 
        begin
            inc(counth,h[i]);
            dec(i,(i)and(-i));
        end;
end;
    
procedure deal(i:longint);
var j:longint;
begin
    j:=x[i];
    while j<=maxn do 
        begin
            inc(a[j]);
            inc(h[j],x[i]);
            inc(j,j and(-j));
        end;
end;
    
begin
    readln(n);
    for i:=1 to n do readln(v[i],x[i]);
    qsort(1,n);
    for i:=1 to n do 
        begin    
            p:=count(x[i]);
            m:=counth(x[i]);
            inc(ans,v[i]*(p*x[i]-m));
            p:=count(maxn)-p;
            m:=counth(maxn)-m;
            inc(ans,v[i]*(m-p*x[i]));
            deal(i);
        end;
    writeln(ans);
end.