CheckIfWordEqualsSummationOfTwoWords.cpp

// Source : https://leetcode.com/problems/check-if-word-equals-summation-of-two-words/
// Author : Hao Chen
// Date   : 2021-05-30

/***************************************************************************************************** 
 *
 * 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.
 ******************************************************************************************************/

class Solution {
public:
    int strToInt(string& str) {
        int n = 0;
        for(auto& c :str) {
            n = n*10 + c - 'a';
        }
        return n;
    }
    bool isSumEqual(string firstWord, string secondWord, string targetWord) {
        return strToInt(firstWord) + strToInt(secondWord) == strToInt(targetWord);
    }
};