查找—折半查找

该查找只针对于已经排好序的进行查找操作，很有局限性。

 

package com.ufida.practice.suanfa.search;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class BinarySearch {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
         List<Integer> list = new ArrayList<Integer>();
         for (int i = 0; i < 10; i++)
                list.add(i);
         for(int i : list)
             System.out.print(i+"    ");
         System.out.println("~~~~~~~~~~~~~~~~~~~");
         int num = new Random().nextInt(15);
         System.out.println("找到了"+num+"，位置为:"+BinarySearch(list,num));

    }
    
     public static int BinarySearch(List<Integer> list, int key)
     {
         //最低线
         int low = 0;

         //最高线
         int high = list.size() - 1;

         while (low <= high)
         {
             //取中间值
             int middle = (low + high) / 2;

             if (list.get(middle) == key)
             {
                 return middle;
             }
             else
                 if (list.get(middle) > key)
                 {
                     //下降一半
                     high = middle - 1;
                 }
                 else
                 {
                     //上升一半
                     low = middle + 1;
                 }
         }
         //未找到
         return -1;
     }


}