README.md

1352. Product of the Last K Numbers

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 leastk 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

Solutions (Rust)

1. Solution

structProductOfNumbers{products:Vec<i32>,}/**  * `&self` means the method takes an immutable reference. * If you need a mutable reference, change it to `&mut self` instead. */implProductOfNumbers{fnnew() -> Self{Self{products:vec![1],}}fnadd(&mutself,num:i32){match num {0 => self.products.truncate(1), _ => self.products.push(*self.products.last().unwrap()* num),}}fnget_product(&self,k:i32) -> i32{let len = self.products.len();if k > len asi32 - 1{return0;}self.products[len - 1] / self.products[len - 1 - k asusize]}}/** * Your ProductOfNumbers object will be instantiated and called as such: * let obj = ProductOfNumbers::new(); * obj.add(num); * let ret_2: i32 = obj.get_product(k); */