Python 3 solution

def isValid(s):
    dict1 = {}
    for i in s:
        if i in dict1:
            dict1[i] += 1
        else:
            dict1[i] = 1
    dict2 = {}
    for j in dict1.values():
        if j in dict2:
            dict2[j] += 1
        else:
            dict2[j] = 1
    if len(dict2) == 1:
        return "YES"
    if len(dict2) == 2:
        count = list(dict2.keys())
        freqs = list(dict2.values())
        if (count[0] == 1 and freqs[0] == 1) or (count[1] == 1 and freqs[1] == 1):
            return "YES"
        if abs(count[0] - count[1]) == 1 and (freqs[0] == 1 or freqs[1] == 1):
            return "YES"
    return "NO"

include

include

include

using namespace std;

string isValid(string s) { unordered_map charCount;

// Count the frequency of each character in the string
for (char c : s) {
    charCount[c]++;
}

unordered_map<int, int> freqCount;

// Count the frequency of frequencies
for (const auto& pair : charCount) {
    freqCount[pair.second]++;
}

// If there's only one unique frequency, it's already valid
if (freqCount.size() == 1) {
    return "YES";
}

// If there are two unique frequencies, check if we can remove one character
if (freqCount.size() == 2) {
    auto it = freqCount.begin();
    int freq1 = it->first;
    int count1 = it->second;
    ++it;
    int freq2 = it->first;
    int count2 = it->second;

    // Check if we can remove one character to make it valid
    if ((count1 == 1 && (freq1 - 1 == freq2 || freq1 == 1)) || (count2 == 1 && (freq2 - 1 == freq1 || freq2 == 1))) {
        return "YES";
    }
}

// If none of the conditions are met, it's not valid
return "NO";

}

int main() { string s; cin >> s; string result = isValid(s); cout << result << endl; return 0; }

Solution in C#

• Case I was stumped on was 'aaabbbc'. Take away 'c' and it satisfies the conditions. The obvious case for me was 'aaabbbcccc'.

            if(String.IsNullOrEmpty(s))
            {
                return "YES";
            }

            List<char> sorted = s.OrderBy(x => x).ToList();
            List<char> distinctChars = s.Distinct().OrderBy(x => x).ToList();

            Dictionary<char, int> charCounter = new();
            int count = 0;
            foreach(char c in distinctChars)
            {
                count = sorted.Count(x => x == c);
                charCounter.Add(c, count);
            }

            int distinctCharCounts = charCounter.Values.Distinct().Count();

            if (distinctCharCounts == 1)
            {
                return "YES";
            }

            if(distinctCharCounts == 2)
            {
                var equalToCount = charCounter.Where(x => x.Value == count).ToList();
                var notEqualToCount = charCounter.Where(x => x.Value != count).ToList();

                if (equalToCount.Count == 1)
                {
                    if (count - 1 == 0 ||
                        count - 1 == notEqualToCount[0].Value)
                    {
                        return "YES";
                    }
                }
                if (notEqualToCount.Count == 1)
                {
                    if (notEqualToCount[0].Value - 1 == 0 ||
                        notEqualToCount[0].Value - 1 == count)
                    {
                        return "YES";
                    }
                }
            }

            return "NO";

My solution gets 100% on all tests but returns "yes" to the string "aaaabbbbcc" - I believe the testing may be incomplete or incorrect

DON'T READ IF NOT LOOKING FOR SOLUTION my java soln

public static String isValid(String s) {

char[] c = s.toCharArray();
Arrays.sort(c);
int temp=1;
int res=1;//aabbccc
for(int i=1;i<c.length;i++)
{
    if(c[i]==c[i-1])
    {
        temp++;
    }
    else{
       res=temp;
       temp=i;
       break;
    }

}
int i=temp;
int x=1,y=0;
for( ;i<c.length;i++)
{
    if(c[i]==c[i-1])
    {
        temp++;
    }
    else{

    if(Math.abs(res-temp) > 1)
    {
        return "NO";
    }
       if(temp==res)
       {
           x++;
       }
       else{
           y++;
       }
       temp=1;
    }

}
if(temp==res)
       {
           x++;
       }
       else{
           y++;
       }

if(x>1 && y>1)
return "NO";
return "YES";



}