一个数组中只有一个数出现了k次，还有其他的数都出现了m次，k < m ,k > 1,找出只出现了k次的那一个数
不能使用hash表和词频统计的方法，而且必须在O（n）的时间复杂度内找到

import java.util.*;


public class Main {

    public static int test(int[] arr,int k,int m) {
        HashMap<Integer,Integer> map = new HashMap<>();
        for (int num : arr) {
            if (map.containsKey(num)) {
                map.put(num, map.get(num) + 1);
            } else {
                map.put(num, 1);
            }
        }
        int ans = 0;
        for (int num : map.keySet()) {
            if (map.get(num) == k) {
                ans = num;
                break;
            }
        }
        return ans;
    }

    public static int onlyOne(int[] arr,int k ,int m) {
        int[] t = new int[32];
        for (int num:arr) {
            for (int i = 0;i < 32;i++) {
                t[i] += (num >> i ) & 1;
            }
        }
        int ans = 0;
        for (int i = 0;i < 32;i++) {
            if (t[i] % m != 0) ans |= (1 << i);
        }
        return ans;
    }

    // 为了测试
    public static int[] randomArray(int maxKinds, int range, int k, int m) {
        int ktimeNum = randomNumber(range);
        // 真命天子出现的次数
        int times = k;
        // 2
        int numKinds = (int) (Math.random() * maxKinds) + 2;
        // k * 1 + (numKinds - 1) * m
        int[] arr = new int[times + (numKinds - 1) * m];
        int index = 0;
        for (; index < times; index++) {
            arr[index] = ktimeNum;
        }
        numKinds--;
        HashSet<Integer> set = new HashSet<>();
        set.add(ktimeNum);
        while (numKinds != 0) {
            int curNum = 0;
            do {
                curNum = randomNumber(range);
            } while (set.contains(curNum));
            set.add(curNum);
            numKinds--;
            for (int i = 0; i < m; i++) {
                arr[index++] = curNum;
            }
        }
        // arr 填好了
        for (int i = 0; i < arr.length; i++) {
            // i 位置的数，我想随机和j位置的数做交换
            int j = (int) (Math.random() * arr.length);// 0 ~ N-1
            int tmp = arr[i];
            arr[i] = arr[j];
            arr[j] = tmp;
        }
        return arr;
    }

    // 为了测试
    // [-range, +range]
    public static int randomNumber(int range) {
        return (int) (Math.random() * (range + 1)) - (int) (Math.random() * (range + 1));
    }

    public static void main(String[] args ) throws Exception {
        /*int[] arr = {12,-99,12,12,1,1,1,2,2,2,3,3,3,4,4,4};
        int k = 2,m = 3;
        System.out.println(onlyOne(arr,k,m));*/
        int testTime = 100001, maxlen = 5, range = 30;
        int max = 9;
        System.out.println("测试开始");
        int[] arr = new int[range];
        int num1 = 0,num2 = 0;
        for (int i = 0; i < testTime; i++) {
            int a = (int) Math.random() * max + 1;
            int b = (int) Math.random() * max + 1;
            int k = Math.min(a, b);
            int m = Math.max(a, b);
            if (k == m) {
                m++;
            }

            arr = randomArray(maxlen, range, k, m);
            num1 = onlyOne(arr, k, m);
            num2 = test(arr, k, m);
            if (num1 != num2) {
                System.out.println("程序出错了");
            }

        }
        for (int num:arr) {
            System.out.printf("%d ",num);
        }
        System.out.println();
        System.out.println("测试结束！！！");
        System.out.printf("test: %d\n",num1);
        System.out.printf("onlytest: %d\n",num2);
//    public static int[] RandomArray(int maxlen,int range) {
//        return null;
//    }

    }
}