第三次作业——顺序查找，二分查找

来源：互联网发布：网络流行年轻群体文化编辑：程序博客网时间：2024/05/22 03:00

import java.io.BufferedReader;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.Scanner;

public class Search {
   public static void main(String[] args) {
       // TODO Auto-generated method stub
       int searchNum;//要查询的数字
       int signOne,signTwo;//用来判断
       int readNum;//存放文本转化的数字

       System.out.print("请输入要查找的数据：");
       Scanner scan = new Scanner(System.in);
       searchNum = scan.nextInt();

       try{
           FileReader f = new FileReader("C:/Users/Y470/Desktop/largeW_bubble.txt");
           BufferedReader br = new BufferedReader(f);

           ArrayList arraylist = new ArrayList();
           String line = br.readLine();
           while (line != null) {
               readNum = Integer.parseInt(line.trim());
               arraylist.add(readNum);
               line = br.readLine();
           }
           int array[] = new int[arraylist.size()];//存放从文本读出来的数据

           for(int i=0;i<array.length;i++){
               array[i] = (Integer) arraylist.get(i);
           }

           //顺序查找
           signOne = SSearch(array,array.length-1,searchNum);
           if(signOne == 0){
               System.out.print("顺序查找：");
               System.out.println("数据"+array[signOne]+"查不到");
           }
           //二分查找
           signTwo = BSearch(array,1,array.length-1,searchNum);

           if(signTwo == 0){
               System.out.print("二分查找：");
               System.out.println("数据"+array[signTwo]+"查不到");
           }
           br.close();

       }catch(Exception e){
           e.printStackTrace();
       }
   }
   //顺序查找
   public static int SSearch(int arr[],int high, int target ){
       int i = high;
       arr[0] = target;
       while(arr[i] != target){
           i--;
       }
       return i;
   }
   //二分查找
   public static int BSearch(int arr[],int low,int high,int target){
       int mid;
       if(low>high)
           return 0;
       else{
           mid = (low+high)/2;
           if(target<arr[mid]){
               return BSearch(arr,low,mid-1,target);
           }
           else if(target>arr[mid]){
               return BSearch(arr,mid+1,high,target);
           }
           else
               return mid;
       }
   }

}

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