二分查找

#include <stdio.h>
#define N 6
int f(int a[],int low,int high,int x)
{
int mid =(low+high)/2 ;
if (low>high)      return -1 ;
else     if (a[mid]==x)     return mid ;
else     if (a[mid]>x )     return  f(a,low,mid-1,x);
else            return  f(a,mid+1, high,x);

}
int main ( )
{

int x, a
={ 1,2,3,5,6,7} ;
scanf("%d",&x);
printf("%d\n",f(a,0,N-1,x));

}

********************************************************

#include <stdio.h>
#define N 6
int f(int a[],int low,int high,int x)
{
int mid =(low+high)/2 ;
if(low>high)      return -1 ;
if(a[mid]==x)     return mid ;
if(a[mid]>x)    return  f(a,low,mid-1,x);
else            return  f(a,mid+1, high,x);

}
int main ( )
{

int x, a
={ 1,2,3,5,6,7} ;
scanf("%d",&x);
printf("%d\n",f(a,0,N-1,x));

}