LeetCode [1352] Product of the Last K Numbers

 1352. Product of the Last K Numbers

Medium

Implement the class ProductOfNumbers that supports two methods:

1. add(int num)

• Adds the number num to the back of the current list of numbers.

2. getProduct(int k)

• Returns the product of the last k numbers in the current list.
• You can assume that always the current list has at least k numbers.

At any time, the product of any contiguous sequence of numbers will fit into a single 32-bit integer without overflowing.

 

Example:

Input
["ProductOfNumbers","add","add","add","add","add","getProduct","getProduct","getProduct","add","getProduct"]
[[],[3],[0],[2],[5],[4],[2],[3],[4],[8],[2]]

Output
[null,null,null,null,null,null,20,40,0,null,32]

Explanation
ProductOfNumbers productOfNumbers = new ProductOfNumbers();
productOfNumbers.add(3);        // [3]
productOfNumbers.add(0);        // [3,0]
productOfNumbers.add(2);        // [3,0,2]
productOfNumbers.add(5);        // [3,0,2,5]
productOfNumbers.add(4);        // [3,0,2,5,4]
productOfNumbers.getProduct(2); // return 20. The product of the last 2 numbers is 5 * 4 = 20
productOfNumbers.getProduct(3); // return 40. The product of the last 3 numbers is 2 * 5 * 4 = 40
productOfNumbers.getProduct(4); // return 0. The product of the last 4 numbers is 0 * 2 * 5 * 4 = 0
productOfNumbers.add(8);        // [3,0,2,5,4,8]
productOfNumbers.getProduct(2); // return 32. The product of the last 2 numbers is 4 * 8 = 32 

 

Constraints:

• There will be at most 40000 operations considering both add and getProduct.
• 0 <= num <= 100
• 1 <= k <= 40000

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class ProductOfNumbers { List<Integer> list = new ArrayList<>(); public ProductOfNumbers() { } public void add(int num) { if(num==0) list.clear(); else if(list.isEmpty()){ list.add(num); }else{ list.add(list.get(list.size()-1)*num); } } public int getProduct(int k) { if(k>list.size()) return 0; if(k==list.size()) return list.get(list.size()-1); return list.get(list.size()-1)/list.get(list.size()-1-k); } } /** * Your ProductOfNumbers object will be instantiated and called as such: * ProductOfNumbers obj = new ProductOfNumbers(); * obj.add(num); * int param_2 = obj.getProduct(k); */