#1880: Check if Word Equals Summation of Two Words; solution & tests

Author: vetalapo

c-sharp/Problems/arrays-and-hashing/CheckIfWordEqualsSummationOfTwoWords.cs

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+/**
+ * 1880
+ * Check if Word Equals Summation of Two Words
+ **
+ * The letter value of a letter is
+ * its position in the alphabet starting from 0
+ * (i.e. 'a' -> 0, 'b' -> 1, 'c' -> 2, etc.).
+ *
+ * The numerical value of some string of lowercase English letters s
+ * is the concatenation of the letter values of each letter in s,
+ * which is then converted into an integer.
+ *
+ * For example,
+ * if s = "acb",
+ * we concatenate each letter's letter value,
+ * resulting in "021".
+ * After converting it, we get 21.
+ * You are given three strings
+ * firstWord, secondWord, and targetWord,
+ * each consisting of lowercase English letters 'a' through 'j' inclusive.
+ *
+ * Return true
+ * if the summation of the numerical values of firstWord and secondWord equals
+ * the numerical value of targetWord,
+ * or false otherwise.
+ *
+ * Example 1:
+ *   Input: firstWord = "acb", secondWord = "cba", targetWord = "cdb"
+ *   Output: true
+ *   Explanation:
+ *     The numerical value of firstWord is "acb" -> "021" -> 21.
+ *     The numerical value of secondWord is "cba" -> "210" -> 210.
+ *     The numerical value of targetWord is "cdb" -> "231" -> 231.
+ *     We return true because 21 + 210 == 231.
+ *
+ * Example 2:
+ *   Input: firstWord = "aaa", secondWord = "a", targetWord = "aab"
+ *   Output: false
+ *   Explanation:
+ *     The numerical value of firstWord is "aaa" -> "000" -> 0.
+ *     The numerical value of secondWord is "a" -> "0" -> 0.
+ *     The numerical value of targetWord is "aab" -> "001" -> 1.
+ *     We return false because 0 + 0 != 1.
+ *
+ * Example 3:
+ *   Input: firstWord = "aaa", secondWord = "a", targetWord = "aaaa"
+ *   Output: true
+ *   Explanation:
+ *     The numerical value of firstWord is "aaa" -> "000" -> 0.
+ *     The numerical value of secondWord is "a" -> "0" -> 0.
+ *     The numerical value of targetWord is "aaaa" -> "0000" -> 0.
+ *     We return true because 0 + 0 == 0.
+ *
+ * Constraints:
+ *   • 1 <= firstWord.length, secondWord.length, targetWord.length <= 8
+ *   • firstWord, secondWord, and targetWord consist of lowercase English letters from 'a' to 'j' inclusive.
+ *
+ * Hint 1:
+ *   Convert each character of each word to its numerical value.
+ *
+ * Hint 2:
+ *   Check if the numerical values satisfies the condition.
+ **
+ * https://leetcode.com/problems/check-if-word-equals-summation-of-two-words/
+***/
+
+namespace Problems;
+
+public class CheckIfWordEqualsSummationOfTwoWords
+{
+    public bool IsSumEqual( string firstWord, string secondWord, string targetWord )
+    {
+        return LetterValue( firstWord ) + LetterValue( secondWord ) == LetterValue( targetWord );
+    }
+
+    private int LetterValue( string word )
+    {
+        int result = 0;
+
+        foreach ( char c in word )
+        {
+            result = result * 10 + ( c - 'a' );
+        }
+
+        return result;
+    }
+}

c-sharp/Tests/arrays-and-hashing/CheckIfWordEqualsSummationOfTwoWordsTests.cs

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+using NUnit.Framework;
+
+using Problems;
+
+public class CheckIfWordEqualsSummationOfTwoWordsTests
+{
+    [TestCase( "acb", "cba", "cdb", ExpectedResult = true )]
+    [TestCase( "aaa", "a", "aab", ExpectedResult = false )]
+    [TestCase( "aaa", "a", "aaaa", ExpectedResult = true )]
+    public bool IsSumEqualTest( string firstWord, string secondWord, string targetWord ) =>
+        new CheckIfWordEqualsSummationOfTwoWords().IsSumEqual( firstWord, secondWord, targetWord );
+}