二分查找

二分查找
1.二分查找的基本思想:首先将结点按关键字排序,其次将查找值与中间位置的值比较,相等,查找成功;不等,则中间数据大于或小于查找值,无论怎样查找将在一半的数据中查找。

2.例:输入序列数据查找指定值.

程序:

program sxcz;

const n=7;

type

arr=array[1..n]of integer;

varx1,i:integer;

a:arr;

place:integer;

procedurepaixv(var r:arr;m:integer);

var k,j,i,t:integer;

begin

k:=m;

while k>0 do

begin

j:=k-1;k:=0;

for i:=1 to jdo

ifr>r[i+1] then

begint:=r;a:=r[i+1];r[i+1]:=t;k:=i;end;

end;

end;

proceduresearch(r:arr;m,x:integer; var p:integer);

varlow,high,mid:integer;

begin

p:=0;low:=1;high:=m;

whilelow<=high do

begin

mid:=(low+high)div 2;

if x>r[mid]then low:=mid+1 else

if x<r[mid]then high:=mid-1 else

beginp:=mid;exit;end;

end;

end;

begin

write('Enterarray:');

for i:=1 to ndo read(a);

writeln;

write('Entersearch data:');

read(x1);

paixv(a,n);

search(a,n,x1,place);

ifplace<>0 then writeln('yes') else writeln('no');

end.