# 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 `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.

## 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).