PKU1804 brainman

       这道题让我们模拟冒泡排序，求交换次数，本质上是求序列的逆序对个数。

       我们有两种方法求解——归并排序和树状数组。

 

【归并排序】

 

program Brainman;const maxn=1005; inf=10000000; msg='Scenario #';type arr=array[0..maxn] of longint;var data:arr; n,ans:longint; flag:boolean;procedure prework;begin ans:=0;end;procedure init;var i:longint;begin read(n); for i:=1 to n do read(data[i]);end;procedure mergeit(left,mid,right:longint; var data:arr);var b,c:arr; i,j,k,nb,nc:longint;begin nb:=mid+1-left; nc:=right-mid; for i:=left to mid do b[i+1-left]:=data[i]; for i:=mid+1 to right do c[i-mid]:=data[i]; b[nb+1]:=inf; c[nc+1]:=inf; i:=1; j:=1; for k:=left to right do if b[i]<=c[j] then begin data[k]:=b[i]; inc(i); end else begin data[k]:=c[j]; inc(ans,nb+1-i); inc(j); end;end;procedure msort(left,right:longint; var data:arr);var mid:longint;begin if left<>right then begin mid:=(left+right) shr 1; msort(left,mid,data); msort(mid+1,right,data); mergeit(left,mid,right,data); end;end;procedure outit(i:longint);begin if flag then writeln else flag:=true; writeln(msg,i,':'); writeln(ans);end;procedure bigmain;var i,t:longint;begin readln(t); flag:=false; for i:=1 to t do begin prework; init; msort(1,n,data); outit(i); end;end;begin assign(input,'a.in'); reset(input); assign(output,'a.out'); rewrite(output); bigmain; close(input); close(output);end.

 

 

 

 

【树状数组】

program Brainman;const maxn=2000005; anum=1000002; msg='Scenario #';var c:array[0..maxn] of longint; n,ans:longint; flag:boolean;function lowbit(x:longint):longint;begin exit(x and (-x));end;procedure add(x:longint);begin while x<=maxn do begin inc(c[x]); inc(x,lowbit(x)); end;end;function sum(x:longint):longint;begin sum:=0; while x>0 do begin inc(sum,c[x]); dec(x,lowbit(x)); end;end;procedure prework;begin ans:=0; fillchar(c,sizeof(c),0);end;procedure init;begin read(n);end;procedure main;var i,w:longint;begin for i:=1 to n do begin read(w); inc(w,anum); add(w); inc(ans,sum(maxn)-sum(w)); endend;procedure outit(i:longint);begin if flag then writeln else flag:=true; writeln(msg,i,':'); writeln(ans);end;procedure bigmain;var i,t:longint;begin readln(t); flag:=false; for i:=1 to t do begin prework; init; main; outit(i); end;end;begin assign(input,'a.in'); reset(input); assign(output,'a.out'); rewrite(output); bigmain; close(input); close(output);end.