二分查找（折半查找）

#include<stdio.h>

int dinarysearch(int arr[],int left,int right,int value)

{

int middle=(left+right)/2;

if(left>right)

return -1;

if(value>arr[middle])

return dinarysearch(arr,middle+1,right,value);

if(value<arr[middle])

return dinarysearch(arr,left,middle-1,value);

if(value==arr[middle])

return middle;

}

int main()

{

int arr[]={1,2,3,4,5,6,7};

int value=2;

int i=dinarysearch(arr,0,6,value);

printf("%d\n",i);

getch();

return 0;

}

改进，修改middle的取值，插值查找：

int x=(value-arr[left])/(arr[right]-arr[left]);

int middle=left+x*(right-value);