https://www.hackerrank.com/challenges/sherlock-and-valid-string/problem

SherlockAndTheValidString.cpp

#include <bits/stdc++.h>

using namespace std;

// Complete the isValid function below.
string isValid(string s) {
    // 23:21 THA 25/02/2019
    // by BingLi224
    // Reference: https://www.hackerrank.com/challenges/sherlock-and-valid-string/problem
    
    unsigned long count [ 26 ] = { 0 };
    int idx = 0;
    unsigned long sz = s.length ( );
    for ( idx = 0; idx < sz; idx ++ ) {
        count [ s [ idx ] - 'a' ] ++;
    }

    // skip existing data
    for ( idx = 0; idx < 26 && count [ idx ] == 0; idx ++ ) { }

    if ( idx >= 26 )
        return "YES";    // no data

    // evaluate

    unsigned long minCount, maxCount, min, max;
    minCount = maxCount = count [ idx ];
    min = max = 1;

    for ( ++ idx; idx < 26; idx ++ ) {
        unsigned long c = count [ idx ];
        if ( c <= 0 )
            continue;
        else if ( c == minCount ) {
            min ++;

            if ( c == maxCount ) {
                max ++;
            } else if ( ( max > 1 || maxCount - minCount > 1 ) && ( minCount > 1 || min > 1 ) ) { // && min > 1
                return "NO";
            }
        } else if ( c == maxCount ) {
            max ++;
            if ( minCount > 1 || min > 1 )  // && max > 1
                return "NO";
        } else if ( c < minCount ) {
            if ( minCount < maxCount ) // && ( max > 1 || min > 1 ) ) //&& min > 0 )
                return "NO";    // too high range
            else if ( maxCount - c > 1 && c > 1 )
                return "NO";

            minCount = c;
            min = 1;
        } else if ( c > maxCount ) {
            if ( minCount < maxCount ) //&& max > 0 && min > 0 )
                return "NO";    // too high range
            else if ( c - minCount > 1 && ( min > 1 || minCount > 1 ) )
                return "NO";
            maxCount = c;
            max = 1;

        } else {
            // out of scope
            //cout << minCount << " " << min << " | " << maxCount << " " << max << endl;
            return "NO";
        }

    }
    return "YES";
}

int main()
{
    ofstream fout(getenv("OUTPUT_PATH"));

    string s;
    getline(cin, s);

    string result = isValid(s);

    fout << result << "\n";

    fout.close();

    return 0;
}