二分法查找

#include <stdio.h>
#include <stdlib.h>
/*数组需预先排序*/
/*递归实现*/
int find1( float a[], int start, int end, float tofind)
{
	int center = (start + end)/2;
	if( start > end ) return -1;
	if ( a[center] == tofind ) return center;
	else if( a[center] > tofind )
		find1( a, start, center-1, tofind);
	else
		find1( a, center+1, end, tofind);
}

/*非递归实现*/
int find2( float a[], int start, int end, float tofind)
{
	while ( start <= end )
	{
		int center = ( start + end ) / 2;
		if ( a[center] == tofind )
			return center;
		else if ( a[center] > tofind )
			end = center - 1;
		else
			start = center + 1;
	}
	return -1;
}

int main()
{
	float a[10] = {0,1,2,3,4,5.5,6,7,8,9};
	int pos;
	pos = find2( a, 2, 9, 5.5);
	printf("%d\n",pos);
　　pos = find1( a, 2, 9, 5.5);
　　printf("%d\n",pos);
	return 0;
}