The challenge

Compare two strings by comparing the sum of their values (ASCII character code).

  • For comparing treat all letters as UpperCase
  • null should be treated as empty strings
  • If the string contains other characters than letters, treat the whole string as it would be empty

Your method should return true, if the strings are equal and false if they are not equal.

Examples:

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"AD", "BC"  -> equal
"AD", "DD"  -> not equal
"gf", "FG"  -> equal
"zz1", ""   -> equal (both are considered empty)
"ZzZz", "ffPFF" -> equal
"kl", "lz"  -> not equal
null, ""    -> equal

The solution in Java code

Option 1:

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public class Solution {
  public static boolean compare(String s1, String s2) {
    if (s1==null || s2==null) return true;
    
    s1 = s1.replaceAll(" ", "").toUpperCase().trim();
    s2 = s2.replaceAll(" ", "").toUpperCase().trim();
    
    if (s1.length()==0 || s2.length()==0) return true;
    
    int s1v = 0;
    int s2v = 0;
    
    for(int i=0;i<s1.length(); i++) {
      if (!Character.isAlphabetic(s1.charAt(i))) return true;
      s1v += (int) s1.charAt(i);
    }
    for(int j=0;j<s2.length(); j++) {
      if (!Character.isAlphabetic(s2.charAt(j))) return true;
      s2v += (int) s2.charAt(j);
    }
    
    return s1v==s2v;
  }
}

Option 2:

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public class Solution {

  public static boolean compare(String s1, String s2) {
  
    if (s1 == null || !s1.matches("[a-zA-Z]+")) s1 = "";
    if (s2 == null || !s2.matches("[a-zA-Z]+")) s2 = "";
    
    return s1.toUpperCase().chars().sum() == s2.toUpperCase().chars().sum();
  }
}

Option 3:

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class Solution {
  static boolean compare(String s1, String s2) {
    return (s1 != null && s1.matches("[a-zA-Z]+") ? s1.toUpperCase().chars().sum() : 0)
        == (s2 != null && s2.matches("[a-zA-Z]+") ? s2.toUpperCase().chars().sum() : 0);
  }
}

Test cases to validate our solution

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import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;

public class SolutionTests {
    @Test
    public void BasicTests() {
        assertEquals("'AD' vs 'BC'", true, Solution.compare("AD", "BC"));
        assertEquals("'AD' vs 'DD'", false, Solution.compare("AD", "DD"));
        assertEquals("'gf' vs 'FG'", true, Solution.compare("gf", "FG"));
        assertEquals("'Ad' vs 'DD'", false, Solution.compare("Ad", "DD"));
        assertEquals("'zz1' vs ''", true, Solution.compare("zz1", ""));
        assertEquals("'ZzZz' vs 'ffPFF'", true, Solution.compare("ZzZz", "ffPFF"));
        assertEquals("'kl' vs 'lz'", false, Solution.compare("kl", "lz"));
        assertEquals("'[null]' vs ''", true, Solution.compare(null, ""));
        assertEquals("'!!' vs '7476'", true, Solution.compare("!!", "7476"));
        assertEquals("'##' vs '1176'", true, Solution.compare("##", "1176"));
    }
    
    @Test
    public void RandomTests() {
      for(int i=0; i < 40; i++) {
        char letter1 = (char)(Math.random() * 26 + 65);
        char letter2 = '1';
  
        do {
          letter2 = (char)(Math.random() * 26 + 65);
        }
        while(letter1 == letter2);
    
        if(Math.random() < 0.5) {
          assertEquals(true, Solution.compare(new String(new char[5]).replace('\0',letter1).toUpperCase() + letter2, letter2 + new String(new char[5]).replace('\0',letter1).toLowerCase()));
        }
        if(Math.random() < 0.5) {
          assertEquals(false, Solution.compare(new String(new char[4]).replace('\0', letter1).toUpperCase() + letter2 + letter2, letter2 + new String(new char[4]).replace('\0', letter1).toLowerCase()));
        }
      }
    }
}