js 二分查找的遞歸和while寫法

1.遞歸
主要是控制三個變量 start end mid ,開始 結束 中間，反覆就ok了。

const data = [18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1]


function Recursive(s,data){

	let len = data.length
	let start = 0
	let end = len-1
	let mid
	return find(start,end,s)

}
function find(start,end,s){

       mid =Math.ceil((end+start)/2) 
     		
	    if (s==data[mid]) {
   	
	    	return s
	    }
	     else if(s>data[mid] && start <= end) {

	    	end = mid-1
	    	return find(start,end,s)
	    }
	    else if(s<data[mid] && start <= end){
         
         start  = mid+1

          return  find(start,end,s)

	    }
	    else{

	    	return null
	    }

}
let v = find(0,15,data)
console.log("vvvv",v)

2. while循環

const data = [18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1]
function while_find(s){
    let len = data.length
	let start = 0
	let end = len-1
	let mid

	while(start <= end){

		mid =Math.ceil((end+start)/2)

		if (s<data[mid]) {

			start = mid+1
		}
		else if(s>data[mid]){
			end = mid-1 
		}
		else{

			return s
		}


	}

  return null
}
let v= while_find(8)
console.log("vvvv",v)

主要借鑑了這篇文章 點擊打開 裏面還有一些二分算法的變形， 感興趣的同學可以去看看 寫的很棒。