C语言之二分法查找

#include 

int binary( int *a, int key, int n )
{
    int left = 0, right = n - 1, mid = 0;
    mid = ( left + right ) / 2;

    while( left < right && a[mid] != key )
    {
        if( a[mid] < key ) {
        	left = mid + 1;
        }else if( a[mid] > key ) {
            right = mid - 1;
        }else {
        	return mid;
        }
        mid = ( left + right ) / 2;
    }
    if( a[mid] == key )   return mid;
    return -1;
}

int main(void)
{

	int a[] = {1,2,3,4,5,6,7,8,9,12,13,45,67,89,99,101,111,123,134,565,677};
	int b[] = { 677, 1, 7, 11, 67 };

	int i;
	for( i=0; i < sizeof(b)/sizeof(b[0]);i++)
	{
		printf( "%d\n", binary( a, b[i], sizeof(a)/sizeof(a[0])));
	}

	printf("【说明：-1表示在源数组中不存在要查找的key，其他值表示在源数组中的下标】\n");

	return 0;
}