2665. Counter II | leetcode

2665. Counter II 題目

Write a function createCounter. It should accept an initial integer init. It should return an object with three functions.
編寫函式 createCounter。它應該接受初始整數 init。返回一個具有三個函式的物件。

• increment() increases the current value by 1 and then returns it.
  increment() 將當前值增加 1，然後返回它。
• decrement() reduces the current value by 1 and then returns it.
  decrement()將當前值減小 1，然後返回它。
• reset() sets the current value to init and then returns it.
  reset() 將當前值設置為 init，然後返回它。

Example 1:

Input: init = 5, calls = ["increment","reset","decrement"]
Output: [6,5,4]
Explanation:
const counter = createCounter(5);
counter.increment(); // 6
counter.reset(); // 5
counter.decrement(); // 4

Example 2:

Input: init = 0, calls = ["increment","increment","decrement","reset","reset"]
Output: [1,2,1,0,0]
Explanation:
const counter = createCounter(0);
counter.increment(); // 1
counter.increment(); // 2
counter.decrement(); // 1
counter.reset(); // 0
counter.reset(); // 0

Constraints:

• -1000 <= init <= 1000
• 0 <= calls.length <= 1000
• calls[i] is one of "increment", "decrement" and "reset"

解法參考

var createCounter = function(init) {
	let currentValue = init;
  return {
  	increment: () => currentValue+=1,
   	decrement: () => currentValue-=1,
   	reset: () => currentValue = init,
  }
};

var createCounter = function(init) {
	let currentValue = init;
  return {
  	increment: () => ++currentValue,
   	decrement: () => --currentValue,
   	reset: () => currentValue = init,
  }
};

不能寫 currentValue++ / currentValue--，因為會先回傳 currentValue，才進行 ++ / --。

或改寫成 進行 currentValue++ 後，再 return

var createCounter = function(init) {
	let currentValue = init;
  return {
  	increment: () => {
        currentValue++
        return currentValue;
    },
   	decrement: () => {
        currentValue--;
        return currentValue;
    },
   	reset: () => currentValue = init,
  }
};