今天我们写一个选择法排序与折半查找法相结合的程序。主要实现先排序在查找。前面我们已经详细的讲过了选择排序法，现在我们来说下折半查找法。
折半查找法的主要思想是 number与mid的比较
mid = （butt+top）/2
如果number大于mid，则top = mid+1；
如果number小于mid，则butt = mid-1；
下面附上我的代码，如有不合理的地方，请指正！
#include <stdio.h>
#define N 15
void binsearch(int a[N])/*折半查找*/
{
int top;
int but;
int mid;
int flag;
int num;
int sign;
int loca;
char c;
flag = 1;
while(flag)
{
printf("input the number you want to search!");
scanf("%d",&num);
top = 0;
sign = 0;
but = N - 1;
if((num < a[0]) && (num >a[N-1]))
{
loca = -1;
}
while((!sign) && (top <= but))
{
mid = (top + but)/2;
if(num == a[mid])
{
loca = mid;
printf("Has found the number %d,its postion is %d\n",num,loca + 1);
sign = 1;
}
else if(num > a[mid])
{
top = mid +1;
}
else
{
but = mid -1;
}
}
if(!sign || loca == -1)
{
printf("Can not find the number!\n");
}
printf("continue or no [Y/N]:\n");
scanf(" %c",&c);
if(c == 'N' || c == 'n')
{
flag = 0;
}
}
}
void choicearrange(int a[N])/*选择法排序*/
{
int i;
int j;
int k;
int temp;
for(i = 0; i < N-1; i++)
{
k = i;
for(j = i + 1; j < N; j++)
{
if(a[k] > a[j])
{
k = j;
}
}
if(k != i)
{
temp = a[k];
a[k] = a[i];
a[i] = temp;
}
}
}
int main()/*主函数*/
{
int a[N];
int i;
for(i = 0; i < N; i++)
{
scanf("%d",&a[i]);
}
choicearrange(a);
for(i = 0 ;i < N; i++)
{
printf("%-3d",a[i]);
}
printf("\n");
binsearch(a);
return 0;
}
程序运行结果见下图：
