超过一半的数字

题目

数组中有一个数字的出现的次数超过了数组长度的一半，找出这个数字

解法1

统计每个数字出现次数

package com.company;

import java.util.Arrays;

public class Test23 {
    public static void main(String[] args) {
        int[] arr={5,20,5,5,69,5,5};

        //求69这个最大值
        int max=arr[0];
        for (int i = 1; i < arr.length; i++) {
            if(arr[i]>max){
                max=arr[i];
            }
        }
        System.out.println( max );
        //70的下标数组
        int[] index=new int[max+1];

        for (int i = 0; i < arr.length; i++) {
            index[arr[i]]++;
        }
        System.out.println(Arrays.toString(index));

        int half=0;
        if(arr.length%2==0){
            half=arr.length/2;
        }else{
            half=arr.length/2+1;
        }
        System.out.println(half);

        for (int i = 0; i < index.length; i++) {
            if(index[i]>half){
                System.out.println(i);
                break;
            }
        }


    }
}

解法2

先排序，中间值就是答案。
为了练练手，用的基数排序

package com.company;

import com.company.util.ArrayUtil;

import java.util.ArrayList;
import java.util.Arrays;

public class Test22 {
    public static void main(String[] args) {
        int[] arr={5,20,5,5,69,5};

//        int[] arr = ArrayUtil.randomArray(1, 1000, 10);
        ArrayList<Integer>[] barrel=new ArrayList[10];
        for (int i = 0; i < barrel.length; i++) {
            barrel[i]=new ArrayList<>();
        }
//        barrel[0]=new ArrayList<>();
//        barrel[0].add(10);
//        System.out.println(barrel[0].get(0));

        for (int k = 0; k <3 ; k++) {
            for (int i = 0; i < arr.length; i++) {
                int temp=arr[i];
                for (int j = 0; j < k; j++) {
                    temp/=10;
                }
                int num=temp%10;
                barrel[num].add(arr[i]);
            }
            printBarrel(barrel);

            int j=0;
            for (int i = 0; i < barrel.length; i++) {
                for (Integer num:barrel[i]){
                    arr[j]=num;
                    j++;
                }
            }
            System.out.println(Arrays.toString(arr));

            for (int i = 0; i < barrel.length; i++) {
                barrel[i].clear();
            }
        }
        System.out.println(arr[arr.length/2]);






    }
    public static void printBarrel(ArrayList<Integer>[] barrel){
        for (int i = 0; i < barrel.length; i++) {
            System.out.println("桶"+i+":");
            for (Integer num:barrel[i]){
                System.out.print(num+" ");
            }
            System.out.println();
        }
    }
}