二分查找（遞歸、非遞歸）和斐波那契數列

package Suanfa;

public class 二分查找和斐波那契數列 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int []arr={1,2,3,6,7,8};
		int index=二分查找遞歸(arr,9,0,arr.length);
		System.out.println(index);
	}
	//二分查找非遞歸實作
	public static int 二分查找非遞歸(int []arr,int key) {
		int start=0,end=arr.length-1;
		while(start<=end){
			int mid=(start+end)/2;
			//注意mid+1和mid-1，否則找不到會發生無限循環
			if(key>arr[mid]){
				start=mid+1;
			}else if(key<arr[mid]){
				end=mid-1;
			}else if(key==arr[mid]){
				return mid;
			}
		}
		return -1;
	}
	//二分查找的遞歸實作
	public static int 二分查找遞歸(int []arr,int key,int start,int end){
		int mid=(start+end)/2;
		if(arr[mid]==key){
			return mid;
		}
		//相等
		if(start>=end){
			return -1;
		}else if(key>arr[mid]){
			return 二分查找遞歸(arr,key,mid+1,end);
		}else if(key<arr[mid]){
			return 二分查找遞歸(arr,key,start,mid-1);
		}
		return -1;
	}
	
	public static int 斐波那契數列(int n) {
		if(n==0){
			return 0;
		}
		if(n==1||n==2){
			return 1;
		}
		int res=0;
		int nums1=1,nums2=1;
		for(int i=3;i<=n;i++){
			res=nums1+nums2;
			nums1=nums2;
			nums2=res;
		}
		return res;
	}

}