折半查找

折半查找

int fun(int *a,int left,int right,int x)
{
	int mid;
	int num=-1;
	mid=(left+right)/2;
	if(left<=right)
	{
		mid=(left+right)/2;
		if (x>a[mid])
		{
			num=fun(a,mid+1,right,x);
		}
		else if (x<a[mid])
		{
			num=fun(a,left,mid-1,x);
		}
		else
		{
			num=mid;
		}
	}
	return num;
	
}