二分搜索

int BinSearch(int k)
{
	int rtn = -1;
	int low=1;
	int high=in[0];
	int mid;

	while(low<=high)
	{
		mid = (low+high)/2;
		if(in[mid]==k)
			rtn = mid;
		if(k>in[mid])
			low = mid+1;
		else
			high = mid-1;		
	}

	return rtn;
}