折半查找

Java代码：

public class binarySearch {
	public static void main(String[] args) {
		// TODO Auto-generated method stub
     int [] arr={1,4,6,9,13,2,98};
     int low = 0;
     int high = arr.length-1;
     int key = 98;
     System.out.println(solution(arr,low,high,key));
	}	
	private static int solution(int [] arr,int low,int high,int key){
		if(low<=high){
			int mid = low +(high-low)/2;
			if(key==arr[mid]){
				return mid;
			}
			else if(key<arr[mid]){
				return solution(arr,low,mid-1,key);				
			}
			else{
				return solution(arr,mid+1,high,key);
			}
		}
		return -1;		
	}
}

输出：6