<script>
var a=new Array(3,6,8,10,12,15,16,18,21,25,30);
//var a=["林大头","王大头","陈大头","张大头","李大头","郑大头","黄大头"]
function seach(n){
var low=0,mid,high=a.length-1;
while( low <= high ){
mid = Math.floor((low + high) / 2);
if (a[mid]==n) return mid;
if (a[mid]<n) low=mid+1;
else high=mid-1;
}
return -1;
}
alert(seach(15));
</script>
java版本的二分法算法实现
/**
文件名:ErFenFa.java
描述:在一个已经排好顺序的数字序列中,找出某个已知数字的位置
作者:慈勤强
Email:cqq1978@Gmail.com
Http://blog.youkuaiyun.com/cqq
**/
class ErFenFa
{
int[] iArray={1,5,9,14,27,39,41,50,62,222,345,612,981,1207,8721}; //在此数字序列中寻找
int iSeek=345; //寻找345的位置
int iCount=0; //比较的次数
public int xunhuan()
//普通的循环法,最少需要比较一次,比如查找1,最多需要比较15次,比如8721
{
for(int i=0;i<iArray.length;i++)
{
iCount++;
if (iSeek==iArray[i])
break;
}
return iCount;
}
public int erfen()
//二分法查找
{
int iIndex=0; //相当于指针的东西
int iStart=0; //
int iEnd=iArray.length-1;
while(true)
{
iCount++;
iIndex = (iStart+iEnd)/2;
if(iArray[iIndex]<iSeek)
{
iStart = iIndex;
}
else if(iArray[iIndex]>iSeek)
{
iEnd = iIndex;
}
else
{
break;
}
}
return iCount;
}
public static void main(String[] args)
{
ErFenFa eff=new ErFenFa();
ErFenFa eff1=new ErFenFa();
System.out.println("普通的循环查找,需要比较的次数:"+eff.xunhuan());
System.out.println("二分法查找,需要比较的次数:"+eff1.erfen());
}
}