二分法查找

public class Search{
	public static void main(String[] args)
	{
		int arr1[] ={1,3,5,6,8,10,13,15,19,23};
		int i = 23;
		System.out.println(binarySearch(arr1,i));
	}
	
	public static int binarySearch(int a[],int num)
	{
		int start = 0;
		int end = a.length - 1;
		int m = (end + start)/2;
		
		while(start<=end)
		{
			if(a[m] == num)
			{
				return m+1;
			}
			if(a[m] > num)
			{
				end = m-1;
			}
			if(a[m] < num)
			{
				start = m+1;
			}
			m = (end + start)/2;
		}
		return -1;
	}
}