SyntaxShelf

Character count

2 snippets across 2 stacks - Interview Prep, SQL

Also written as count characters

DSAInterview Prep

Frequency Counting

DSA · Hash Maps & Sets
Syntax
Build a map of element → count.
Useful for: most common element, anagrams, character counting, voting problems.
Example
// JavaScript
function frequencyMap(arr) {
  const freq = new Map();
  for (const item of arr) {
    freq.set(item, (freq.get(item) || 0) + 1);
  }
  return freq;
}

function mostFrequent(arr) {
  const freq = frequencyMap(arr);
  let maxCount = 0, result = null;
  for (const [key, count] of freq) {
    if (count > maxCount) { maxCount = count; result = key; }
  }
  return result;
}

# Python
from collections import Counter

def frequency_map(arr):
    freq = {}
    for item in arr:
        freq[item] = freq.get(item, 0) + 1
    return freq

def most_frequent(arr):
    return Counter(arr).most_common(1)[0][0]
Output
most_frequent([1,2,2,3,3,3]) → 3

Note Time O(n), Space O(k) where k is unique elements. Python's Counter is a powerful shortcut. In interviews, building the map manually shows understanding. Tie-breaking: clarify with interviewer what to return if multiple elements share max frequency.

SQLSQL

LENGTH / CHAR_LENGTH

SQL · String Functions
Syntax
LENGTH(string)
CHAR_LENGTH(string)
Example
SELECT
  first_name,
  CHAR_LENGTH(first_name) AS name_length
FROM users
WHERE CHAR_LENGTH(first_name) > 10;
Output
-- first_name  | name_length
-- Christopher | 11

Note CHAR_LENGTH counts characters; LENGTH counts bytes. They differ for multi-byte character sets (UTF-8). Use CHAR_LENGTH for user-facing string length. ANSI standard is CHARACTER_LENGTH.

Frequently asked questions

How does Interview Prep handle character count?
This task is covered in 2 stacks on this page: Interview Prep, SQL. The "Frequency Counting" snippet in Interview Prep uses `Build a map of element → count.`.
Which code does the Interview Prep example use?
The "Frequency Counting" snippet uses `Build a map of element → count.`, from the Hash Maps & Sets section of the Interview Prep cheat sheet.
Which stacks cover "character count" on this page?
Interview Prep, SQL. Together they hold 2 copy-ready snippets for this task.
Is there anything to watch out for?
Yes. For "Frequency Counting": Time O(n), Space O(k) where k is unique elements. Python's Counter is a powerful shortcut. In interviews, building the map manually shows understanding. Tie-breaking: clarify with interviewer what to return if multiple elements share max frequency.

Browse all tasks by intent