# CodeSignal Interview – isCryptSolution

## Problem

A *cryptarithm* is a mathematical puzzle for which the goal is to find the correspondence between letters and digits, such that the given arithmetic equation consisting of letters holds true when the letters are converted to digits.

You have an array of strings `crypt`

, the *cryptarithm*, and an an array containing the mapping of letters and digits, `solution`

. The array `crypt`

will contain three non-empty strings that follow the structure: `[word1, word2, word3]`

, which should be interpreted as the `word1 + word2 = word3`

cryptarithm.

If `crypt`

, when it is decoded by replacing all of the letters in the cryptarithm with digits using the mapping in `solution`

, becomes a valid arithmetic equation containing no numbers with leading zeroes, the answer is `true`

. If it does not become a valid arithmetic solution, the answer is `false`

.

**Note** that number `0`

doesn’t contain leading zeroes (while for example `00`

or `0123`

do).

Example

For `crypt = ["SEND", "MORE", "MONEY"]`

and

```
solution = [['O', '0'],
['M', '1'],
['Y', '2'],
['E', '5'],
['N', '6'],
['D', '7'],
['R', '8'],
['S', '9']]
```

the output should be`solution(crypt, solution) = true`

.

When you decrypt `"SEND"`

, `"MORE"`

, and `"MONEY"`

using the mapping given in `crypt`

, you get `9567 + 1085 = 10652`

which is correct and a valid arithmetic equation.

For `crypt = ["TEN", "TWO", "ONE"]`

and

```
solution = [['O', '1'],
['T', '0'],
['W', '9'],
['E', '5'],
['N', '4']]
```

the output should be`solution(crypt, solution) = false`

.

Even though `054 + 091 = 145`

, `054`

and `091`

both contain leading zeroes, meaning that this is not a valid solution.

## Solution

### Idea

I think that this problem is not difficult to solve although it seems pretty complicated. We just need to decompose it to simple pieces and solve one by one.

- Replace characters in
`crypt`

to number from`solution`

. - Check the starting zeroes.
- Check the equation.

### Code

```
function solution(crypt, solution) {
for (let i = 0; i < solution.length; i++) {
for (let ii = 0; ii < crypt.length; ii++) {
crypt[ii] = crypt[ii].replaceAll(solution[i][0], solution[i][1]);
}
}
// test valid number
// should not start with 0
for (let i = 0; i < crypt.length; i++) {
if (/^(?:[1-9][0-9]*|0)$/.test(crypt[i]) === false) {
return false;
}
}
return parseInt(crypt[0]) + parseInt(crypt[1]) === parseInt(crypt[2]);
}
```