二分法查找

public class Demo {
	public static void main(String[] args) {
		System.out.println(search2(new int[]{1,4,5,9,11,23,25,33},7));
	}
	
	public static int search(int[] arr,int key){
		int start=0;
		int end=arr.length-1;
		while(start<=end){
			int middle=(start+end)/2;
			
			if(key<arr[middle]){
				end=middle-1;
			}else if(key>arr[middle]){
				start=middle+1;
			}else{
				return middle;
			}
		}
		return -1;
	}
	
	public static int search2(int[] arr,int key){
		int start=0;
		int end=arr.length-1;
		int middle=(start+end)/2;
		while(arr[middle]!=key){
			
			if(key<arr[middle]){
				end=middle-1;
			}else{
				start=middle+1;
			}
			if(start>=end){
				return -1;
			}
			middle=(start+end)/2;
		}
		return middle;
	}
}