Maximum Equal Frequency in C++

Suppose we have an array nums of positive integers, we have to return the longest possible length of an array prefix of given array nums, such that it is possible to delete exactly one element from this prefix so that every number that has appeared in it will have the same frequency. After removing one element if there are no remaining elements, it's still considered that every appeared number has the same frequency (0).

So, if the input is like [3,3,2,2,6,4,4,6], then the output will be 7, So if we remove element 6 from index 4, then the subarray will be [3,3,2,2,4,4] where all elements appeared two times.

To solve this, we will follow these steps −

maxf := 0, res := 0
Define maps cnt and freq
for initialize i := 0, when i < size of nums, update (increase i by 1), do −
- x := nums[i]
- (increase cnt[x] by 1)
- f := cnt[x]
- (increase freq[f] by 1)
- decrease freq[f - 1] by 1
- maxf := maximum of maxf and f
- if maxf * freq[maxf] is same as i or (maxf - 1) * (freq[maxf - 1] + 1) is same as i or maxf is same as 1, then −
  - res := i + 1
return res

Let us see the following implementation to get better understanding −

Example

Live Demo

#include <bits/stdc++.h>
using namespace std;
class Solution {
   public:
   int maxEqualFreq(vector<int>& nums) {
      int maxf = 0, res = 0;
      map<int, int> cnt, freq;
      for (int i = 0; i < nums.size(); i++) {
         int x = nums[i];
         cnt[x]++;
         int f = cnt[x];
         freq[f]++;
         freq[f - 1]--;
         maxf = max(maxf, f);
         if (maxf * freq[maxf] == i || (maxf - 1) * (freq[maxf - 1] + 1) == i || maxf == 1) {
            res = i + 1;
         }
      }
      return res;
   }
};
main(){
   Solution ob;
   vector<int> v = {3,3,2,2,6,4,4,6};
   cout << (ob.maxEqualFreq(v));
}