Algorithm
30 Days of JavaScript
Counter

2620. Counter

Tags

  • Closures

Link

https://leetcode.com/problems/counter/description/?envType=study-plan-v2&envId=30-days-of-javascript (opens in a new tab)

Question

Given an integer n, return a counter function. This counter function initially returns n and then returns 1 more than the previous value every subsequent time it is called (n, n + 1, n + 2, etc).

Example 1:
Input:
n = 10
["call","call","call"]
Output: [10,11,12]
Explanation:
counter() = 10 // The first time counter() is called, it returns n.
counter() = 11 // Returns 1 more than the previous time.
counter() = 12 // Returns 1 more than the previous time.
Example 2:
Input:
n = -2
["call","call","call","call","call"]
Output: [-2,-1,0,1,2]
Explanation: counter() initially returns -2. Then increases after each sebsequent call.
Constraints:
  • -1000 <= n <= 1000
  • 0 <= calls.length <= 1000
  • calls[i] === "call"

Answer

JavaScript

/**
 * @param {number} n
 * @return {Function} counter
 */
var createCounter = function (n) {
  return function () {
    return n++;
  };
};
 
const counter = createCounter(10);
 
/**
 * const counter = createCounter(10)
 * counter() // 10
 * counter() // 11
 * counter() // 12
 */
/**
 * @param {number} n
 * @return {Function} counter
 */
var createCounter = function (n) {
  counter = -1;
  return function () {
    counter = counter + 1;
    return n + counter;
  };
};
 
/**
 * const counter = createCounter(10)
 * counter() // 10
 * counter() // 11
 * counter() // 12
 */
Compact ObjectCounter Ii