README.md

1381. Design a Stack With Increment Operation

Design a stack which supports the following operations.

Implement the CustomStack class:

• CustomStack(int maxSize) Initializes the object with maxSize which is the maximum number of elements in the stack or do nothing if the stack reached the maxSize.
• void push(int x) Adds x to the top of the stack if the stack hasn't reached the maxSize.
• int pop() Pops and returns the top of stack or -1 if the stack is empty.
• void inc(int k, int val) Increments the bottom k elements of the stack by val. If there are less than k elements in the stack, just increment all the elements in the stack.

Example 1:

Input:
["CustomStack","push","push","pop","push","push","push","increment","increment","pop","pop","pop","pop"]
[[3],[1],[2],[],[2],[3],[4],[5,100],[2,100],[],[],[],[]]
Output:
[null,null,null,2,null,null,null,null,null,103,202,201,-1]
Explanation:
CustomStack customStack = new CustomStack(3); // Stack is Empty []
customStack.push(1);                          // stack becomes [1]
customStack.push(2);                          // stack becomes [1, 2]
customStack.pop();                            // return 2 --> Return top of the stack 2, stack becomes [1]
customStack.push(2);                          // stack becomes [1, 2]
customStack.push(3);                          // stack becomes [1, 2, 3]
customStack.push(4);                          // stack still [1, 2, 3], Don't add another elements as size is 4
customStack.increment(5, 100);                // stack becomes [101, 102, 103]
customStack.increment(2, 100);                // stack becomes [201, 202, 103]
customStack.pop();                            // return 103 --> Return top of the stack 103, stack becomes [201, 202]
customStack.pop();                            // return 202 --> Return top of the stack 102, stack becomes [201]
customStack.pop();                            // return 201 --> Return top of the stack 101, stack becomes []
customStack.pop();                            // return -1 --> Stack is empty return -1.

Constraints:

• 1 <= maxSize <= 1000
• 1 <= x <= 1000
• 1 <= k <= 1000
• 0 <= val <= 100
• At most 1000 calls will be made to each method of increment, push and pop each separately.

Solutions (Rust)

1. Solution

struct CustomStack {
    stack: Vec<i32>,
    max_size: usize,
}


/** 
 * `&self` means the method takes an immutable reference.
 * If you need a mutable reference, change it to `&mut self` instead.
 */
impl CustomStack {

    fn new(maxSize: i32) -> Self {
        Self {
            stack: Vec::with_capacity(maxSize as usize),
            max_size: maxSize as usize,
        }
    }

    fn push(&mut self, x: i32) {
        if self.stack.len() < self.max_size {
            self.stack.push(x);
        }
    }

    fn pop(&mut self) -> i32 {
        self.stack.pop().unwrap_or(-1)
    }

    fn increment(&mut self, k: i32, val: i32) {
        for i in 0..(k as usize).min(self.stack.len()) {
            self.stack[i] += val;
        }
    }
}

/**
 * Your CustomStack object will be instantiated and called as such:
 * let obj = CustomStack::new(maxSize);
 * obj.push(x);
 * let ret_2: i32 = obj.pop();
 * obj.increment(k, val);
 */