位运算很强大很神奇

下面是两段代码

求两数的平均数

 

1 function ave(a,b:longint):longint;
2   begin
3     exit((a and b)+(a xor b)>>1);
4   end;

 

 

求一个十进制数转换成二进制后1的个数

 

function num(n:longint):longint;
  begin
    n:=(n and $55555555)+((n>>1) and $55555555);
    n:=(n and $33333333)+((n>>2) and $33333333);
    n:=(n and $0F0F0F0F)+((n>>4) and $0F0F0F0F);
    n:=(n and $00FF00FF)+((n>>8) and $00FF00FF);
    n:=(n and $0000FFFF)+((n>>16) and $0000FFFF);
    exit(n);
  end;