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.

1880. Check if Word Equals Summation of Two Words
``````struct Solution;

trait NumVal {
fn val(&self) -> i32;
}

impl NumVal for String {
fn val(&self) -> i32 {
let mut res = 0;
for b in self.bytes() {
let x = b - b'a';
res *= 10;
res += x as i32;
}
res
}
}

impl Solution {
fn is_sum_equal(first_word: String, second_word: String, target_word: String) -> bool {
first_word.val() + second_word.val() == target_word.val()
}
}

#[test]
fn test() {
let first_word = "acb".to_string();
let second_word = "cba".to_string();
let target_word = "cdb".to_string();
let res = true;
assert_eq!(
Solution::is_sum_equal(first_word, second_word, target_word),
res
);
let first_word = "aaa".to_string();
let second_word = "a".to_string();
let target_word = "aab".to_string();
let res = false;
assert_eq!(
Solution::is_sum_equal(first_word, second_word, target_word),
res
);
let first_word = "aaa".to_string();
let second_word = "a".to_string();
let target_word = "aaaa".to_string();
let res = true;
assert_eq!(
Solution::is_sum_equal(first_word, second_word, target_word),
res
);
}
``````