4、折半查找

折半查找,提高效率,但是必须要保证该数组是有序排列

 

示例：

class Other 
{
	public static void main(String[] args) 
	{
		int[] arr = new int[]{5,3,6,8,4,6,9,2};
		int pos = halfSearch(arr,9);
		System.out.println(pos);
	}
	public static int halfSearch(int[] arr,int key)
	{
		int min = 0;
		int max = arr.length-1;
		int mid;
		while(min <= max)
		{
			mid =(min + max)/2;
			if(arr[mid] > key) 
				max = mid;
			else if(arr[mid] < key)
				min = mid;
			else
				return mid;
		}
		return -1;
	}
}