LeetCode 1880. Check if Word Equals Summation of Two Words

Description

https://leetcode.com/problems/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 firstWordsecondWord, 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
• firstWordsecondWord, and targetWord consist of lowercase English letters from 'a' to 'j' inclusive.

Explanation

Calculate numerical values for each word and check if two numerical values sum up to the target numerical value.

Python Solution

class Solution:
def isSumEqual(self, firstWord: str, secondWord: str, targetWord: str) -> bool:

first_numerical = self.get_numerical(firstWord)
second_numerical = self.get_numerical(secondWord)
target_numerical = self.get_numerical(targetWord)

return target_numerical == first_numerical + second_numerical

def get_numerical(self, word):

result = 0

for c in word:
result = 10 * result + (ord(c) - ord('a'))

return result
• Time Complexity: O(N).
• Space Complexity: O(1).