def isValid(s): d = {i: s.count(i) for i in s} freqs = list(d.values()) freq_count = [] for f in freqs: if f not in freq_count: freq_count.append(f) if len(freq_count) == 1: return "YES"
elif len(freq_count) == 2: f1, f2 = freq_count if (freqs.count(f1)==1 and f1-f2== 1) or (freqs.count(f2)==1 and f2-f1==1): return "YES" elif (freqs.count(f1)==1 and f1==1) or (freqs.count(f2)==1 and f2==1): return "YES" else: return "NO" else: return "NO"

Through Brute Force:> cpp solution

string isValid(string s) { int freq[26]={0}; for (char c:s) { freq[c-'a']++; }

sort(freq,freq+26);

if ((freq[24]==0) && (freq[25]!=0))
{
    return "YES";
}
int j=0;
while(freq[j]==0)
{
    j++;
}
if (freq[j]==freq[25])
{
    return "YES";
}

else if ((freq[j]==1) &&  freq[j+1]==freq[25])
{
    return "YES";
}

else if((freq[25]-freq[j]==1) && freq[j]==freq[24])
{
    return "YES";
}

else
{
    return "NO";
}

}

string isValid(string s) {

int c=0;

vector<int>vec;

unordered_map<char , int>mp;

for(int i=0;s[i];i++){

    if(mp.find(s[i]) == mp.end())

        mp.insert({s[i],1});

    else

        mp[s[i]]++;

}

for(auto it:mp){

    vec.push_back(it.second);

}

int l=vec[1];

for(int x:vec){

    if(x==l)

        continue;

    else if(x>l||x<l){

        c++;

        continue;

    }

    else

        return "NO";

} } if(c>1 return "NO"; else return "YES";

JavaScript:

function isValid(s: string): string {
  const charFreq = new Map();
  
  for (let char of s) {
    charFreq.set(char, (charFreq.get(char) || 0) + 1);
  }
  
  const freqCount = new Map();
  for (let freq of charFreq.values()) {
    freqCount.set(freq, (freqCount.get(freq) || 0) + 1);
  }
  
  if (freqCount.size === 1) return "YES";
  if (freqCount.size > 2) return "NO";
  
  const [[freq1, count1], [freq2, count2]] = Array.from(freqCount.entries());
  
  // Check valid conditions
  return (
    (freq1 === 1 && count1 === 1) ||
    (freq2 === 1 && count2 === 1) ||
    (Math.abs(freq1 - freq2) === 1 && (count1 === 1 || count2 === 1))
  ) ? "YES" : "NO";
}