Question

How to convert an array of digits to an integer add 1 and convert it back to an array of digits in JavaScript

Answer 1

function convertArrayOfDigitsToIntNumber(arr) {
  let n = 0;
  
  for (let digit of arr) {
    n = n * 10 + digit;
  }
  
  return n;
}

function convertIntNumberToArrayOfDigits(digits, n) {
  let i = digits.length - 1;
  
  while (n > 0) {
    digits[i] = n % 10;
    n = Math.floor(n / 10);
    i--;
  }
}

let arr = [9, 4, 6, 9];

let n = convertArrayOfDigitsToIntNumber(arr);

n++;

convertIntNumberToArrayOfDigits(arr, n);

console.log("n = " + n);
console.log(arr.toString());


 
  
/*
run:
     
n = 9470
9,4,7,0
     
*/

 

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Answer 2

function addOne(arr) {
    for (let i = 0; i < arr.length; i++) {
        if (arr[i] > 9 || arr[i] < -1) return null;
    }
    
    let num = parseInt(arr.join('')) + 1;
    arr = num.toString().split('').map(Number);
    
    return arr;
}


let arr = [9, 4, 6, 9];

arr = addOne(arr);

console.log(arr);


 
  
/*
run:
     
[ 9, 4, 7, 0 ]
     
*/

 

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