查找

package com.lkr.dataStructure;

import java.util.Scanner;

public class Search {

    public static  void main(String[] args){
        int srcArrays[] = {3,5,11,17,21,23,28,30,32,50,64,78,81,95,101};
        Scanner input = new Scanner(System.in);
        System.out.println("请输入你要查找的数：");
        int num = input.nextInt();
        //int seqResult = sequentialSearch(srcArrays,21);
        int seqResult = sequentialSearch(srcArrays,num);
        if(seqResult == -1){
            System.out.println("查找的数不再数组中");
        }
        else {
            System.out.println("顺序查找结果：第" + (seqResult+1) + "个数，值为： " +srcArrays[seqResult] );
        }
        int binResult = binSearch(srcArrays,0, srcArrays.length-1,num);
        if(binResult == -1){
            System.out.println("你要查的数不存在");
        }
        else {

            System.out.println("二分查找结果：第" + (binResult+1) + "个数，值为： " +srcArrays[binResult] );

        }





    }
    //顺序查找算法：从表中的第一个（或最后一个）记录开始，逐个进行记录的关键字和给定值比较，若某个记录的关键字和给定值相等，
    // 则查找成功，找到所查的记录；如果直到最后一个（或第一个）记录，其关键字和给定值比较都不等时，则表中没有多查的记录，查找不成功
    public static int sequentialSearch(int[] a,int value){
        /*int []b = new int[a.length+1];
        b[0] = value;
        for(int i=0;i<a.length;i++){
            b[i+1] = a[i];
        }
        int j = a.length;
        while (b[j] != value){
            j--;
        }

        return j;*/
        for(int i=0;i<a.length;i++){
            if(a[i] == value){
                return i;
            }
        }
        return -1;

    }

    //二分查找递归实现
    public static int binSearch(int[]a,int start,int end,int key){
        int mid = (end - start)/2 +start;
        if(start > end){
            System.out.println("");
            return -1;
        }
        if(key == a[mid]){
            return mid;
        }
        else if(key > a[mid]){
            return binSearch(a,mid+1,end,key);
        }
        else if(key < a[mid]){
            return binSearch(a,start,mid-1,key);
        }
        return -1;
    }


}