How would I replace all '?' in the phrase with a random letter but the letter used cannot-CodePudding

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));

CodePudding user response：

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 ?

CodePudding user response：

I modified your code so that it suits the needs, however there may be some bugs or exceptions not handled yet, but it can give you a hint that how you are going to solve the problem.

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'];

let randomLeter = (excluded) =>
{
   let letter = false;
   do
   {
       letter = letters[Math.floor(Math.random() * 26)];
   }
   while(excluded.includes(letter));
   
   return letter;
}

let getIndices = (s, t) => {
  return [...s].flatMap((char, i) => (char === t ? i : []));
};

let Solve = (riddle) => 
{
    riddle = [...riddle];
    //get the locations of all ? in the string
    let all = getIndices(riddle, '?'); 
    
    for(let i = 0; i < all.length; i  )
    {
        //exluding characters before and after the ?
        let excluded = [riddle[all[i] - 1], riddle[all[i]   1]];

        riddle[all[i]] = randomLeter(excluded);
    }
    
    return riddle.join("");
};

let riddle = 'ab?d?f';
document.getElementById('riddle').innerHTML = 'The Riddle '   riddle;
document.getElementById('solution').innerHTML = "Solution "   Solve(riddle);

<h2 id="riddle"></h2>
<h4 id="solution"></h4>