数组小和，归并排序实现

package com.harrison.class03;
public class Code02_SmallSum {
  public static int smallSum(int[] arr) {
    if (arr == null || arr.length < 2) {
      return 0;
    }
    return process(arr, 0, arr.length - 1);
  }
  public static int process(int[] arr, int L, int R) {
    if (L == R) {
      return 0;
    }
    int mid = L + ((R - L) >> 1);
    return process(arr, L, mid)+
        process(arr, mid + 1, R)+
        merge(arr, L, mid, R);
  }
  public static int merge(int[] arr, int L, int M, int R) {
    int[] help = new int[R - L + 1];
    int i = 0;
    int p1 = L;
    int p2 = M + 1;
    int res=0;
    while (p1 <= M && p2 <= R) {
      res+=arr[p1]<arr[p2]?arr[p1]*(R-p2+1):0;
      help[i++] = arr[p1] < arr[p2] ? arr[p1++] : arr[p2++];
    }
    while (p1 <= M) {
      help[i++] = arr[p1++];
    }
    while (p2 <= R) {
      help[i++] = arr[p2++];
    }
    for (i = 0; i < help.length; i++) {
      arr[L+i] = help[i];
    }
    return res;
  }
  public static int comparator(int[] arr) {
    int res=0;
    if(arr==null || arr.length<2) {
      return 0;
    }
    for(int i=1; i<arr.length;  i++) {
      for(int j=0; j<i; j++) {
        res+=arr[j]<arr[i]?arr[j]:0;
      }
    }
    return res;
  }
  public static int[] generateRandomArray(int maxSize, int maxValue) {
    int[] arr = new int[(int) ((maxSize + 1) * Math.random())];
    for (int i = 0; i < arr.length; i++) {
      arr[i] = (int) ((maxValue + 1) * Math.random()) - (int) (maxValue * Math.random());
    }
    return arr;
  }
  public static int[] copyArray(int[] arr) {
    if (arr == null) {
      return null;
    }
    int[] res = new int[arr.length];
    for (int i = 0; i < arr.length; i++) {
      res[i] = arr[i];
    }
    return res;
  }
  public static void printArray(int[] arr) {
    if (arr == null) {
      return;
    }
    for (int i = 0; i < arr.length; i++) {
      System.out.print(arr[i] + " ");
    }
    System.out.println();
  }
  public static void main(String[] args) {
    int testTimes=1000000;
    int maxSize=100;
    int maxValue=100;
    boolean succeed=true;
    for(int i=0; i<testTimes; i++) {
      int[] arr1=generateRandomArray(maxSize, maxValue);
      int[] arr2=copyArray(arr1);
      if(smallSum(arr1)!=comparator(arr2)) {
        succeed=false;
        printArray(arr1);
        printArray(arr2);
        break;
      }
    }
    System.out.println(succeed?"Nice":"Fucking fucked");
  }
}