Home How would I replace all '?' in the phrase with a random letter but the letter used cannot repeat twice in a row?

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How would I replace all '?' in the phrase with a random letter but the letter used cannot repeat twice in a row?

April 22, 2022

For example say you have the string ‘ab?d?f’ and you must grab the string and replace it with any random letters in the ‘?’ like ‘abcdef’ or ‘abjdlf’ but it cannot be ‘abbdef’ or ‘abcdff’.

I have attempted this below:

const letters = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'];

const randomLeter = () => letters[Math.floor(Math.random() * 26)];

const riddle = 'ab?d?f';

let pickedLetter;
let solvedRiddle;

function solve(riddle) {
    for (let i = 0; i < riddle.length; i++) {
        if (riddle[i] === '?' && !(riddle[i-1] === randomLeter) && !(riddle[i+1] === randomLeter)){
            console.log('Changing to letter');
            solvedRiddle = riddle.replace('?', pickedLetter);
        }
        pickedLetter = randomLeter();
        console.log(i, riddle[i], pickedLetter);
    }
    return solvedRiddle;
}
// The above only returns the first '?' changed but leaves the second one unchanged ... ??? Why can I not change the value of solvedRiddle a second time inside the loop? I can see by my log that it reads at true, but the value won't be re-written.
console.log(solve(riddle));

>Solution :

function solve(riddle) {
    for (let i = 0; i < riddle.length; i++) {
        if (riddle[i] === '?'){
            console.log('Changing to letter');
            let pickedLetter = randomLeter();
            while (riddle[i-1] === pickedLetter || riddle[i+1] === pickedLetter) {
              pickedLetter = randomLeter();
            }
            riddle = riddle.replace('?', pickedLetter);
        }
    }
    return riddle;
}

Also, it’s because u update and return solvedRiddle. Your original riddle string is not updated, so in the second run, it is still changing the first ?