二分查找 （java实现）

package com.li.test01;

import java.util.Scanner;

/**
*
* @author lixiang
*
*/
public class BinarySearch {

//存在返回数组下表，不存在返回-1
//递归实现
public static int binarySearch(int key, int[] array, int low ,int high) {
int mid = low + (high - low) / 2;
if(key < array[low] || key > array[high] || low > high){
return -1;
}

if(key < array[mid]) {
return binarySearch(key, array,low,mid-1);
}
else if(key > array[mid]) {
return binarySearch(key, array, mid+1, high);
}
else {
return mid;
}
}

//非递归实现
public static int binarySearch(int key, int[] array) {
int low = 0;
int high = array.length - 1 ;

while(low <= high) {
int mid = low + (high - low) / 2;
if(key < array[mid]){
high = mid - 1;
}
else if(key > array[mid]) {
low = mid + 1;
}
else {
return mid;
}
}
return -1;
}

public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.println("输入一串有序整数（以逗号分隔） : "); //要查找的数组必须是有序的
int[] intArr = readInts(in.nextLine());
//        Arrays.sort(intArr); //使输入int[]有序
while(true) {
System.out.println("输入要查找数字 : ");
System.out.println(binarySearch(Integer.valueOf(in.nextLine()), intArr, 0, intArr.length-1));
}
}

private static int[] readInts(String str){
String[] strArr = str.split(",");
int[] intArr = new int[strArr.length];
for (int i = 0 ; i < strArr.length; i++) {
intArr[i] = Integer.valueOf(strArr[i]);
}
return intArr;
}
}