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Count Digits in a Number

Given an integer n, return the number of digits present in the number. The number can be positive or negative.

Difficulty:

JavaScript Solution

function countDigits(n) {
  n = Math.abs(n);
  if (n === 0) return 1;
  let count = 0;
  while (n > 0) {
    count++;
    n = Math.floor(n / 10);
  }
  return count;
}

Explanation: We repeatedly divide the number by 10 until it becomes zero, counting each step as one digit.

⏱ O(log n) | 💾 O(1)

Java Solution

class Solution {
  public int countDigits(int n) {
    n = Math.abs(n);
    if (n == 0) return 1;
    int count = 0;
    while (n > 0) {
      count++;
      n /= 10;
    }
    return count;
  }
}

Explanation: Each division by 10 removes one digit from the number.

⏱ O(log n) | 💾 O(1)

Python Solution

def count_digits(n):
    n = abs(n)
    if n == 0:
        return 1
    count = 0
    while n > 0:
        count += 1
        n //= 10
    return count

Explanation: We remove digits one by one using integer division.

⏱ O(log n) | 💾 O(1)

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Count Digits in a Number