java 二分查找算法 - JAVA

编程之美在于算法之美，先来看看二分查找的算法：

隐藏条件：二分查找必须是有序的，从小到大，或从大到小的排序才能进行二分查找，下面来看看代码：

package com.cn.daming;  
  
public class MainActivity {  
      
  
    /** 
     * @param args 
     */  
    public static void main(String[] args) {  
        int[] aInts = new int[]{1,3,5,8,11,14,16,24,37,47,49,56,63,83,223}; //排序是从小到大  
        int[] aInts2 = new int[]{322,243,211,156,98,85,79,68,53,47,38,24,13,6,2}; //排序是从大到小  
        // TODO Auto-generated method stub  
        MainActivity main = new MainActivity();  
        System.out.println("aInts  the reault is : " + main.binarySearch(aInts, 0, aInts.length, 24));  
        System.out.println("aInts2 the reault is : " + main.binarySearch2(aInts2, 0, aInts2.length, 243));  
    }  
  
    //从小到大的二分查找  
    private int binarySearch(int[] a, int start, int len, int key) {  
        int high = start + len, low = start - 1, guess;  
  
        while (high - low >




 1) {  
            guess = (high + low) / 2;  
  
            if (a[guess] < key)  
                low = guess;  
            else  
                high = guess;  
        }  
  
        if (high == start + len)  
            return ~(start + len);  
        else if (a[high] == key)  
            return high;  
        else  
            return ~high;  
    }  
      
    //从大到小的二分查找  
    private int binarySearch2(int[] a, int start, int len, int key) {  
        int high = start + len, low = start - 1, guess;  
  
        while (high - low > 1) {  
            guess = (high + low) / 2;  
  
            if (a[guess] > key)  
                low = guess;  
            else  
                high = guess;  
        }  
  
        if (high == start + len)  
            return ~(start + len);  
        else if (a[high] == key)  
            return high;  
        else  
            return ~high;  
    }  
}