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"]
[,,,[],,,,[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 
customStack.push(2);                          // stack becomes [1, 2]
customStack.pop();                            // return 2 --> Return top of the stack 2, stack becomes 
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 
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.

1381. Design a Stack With Increment Operation
``````struct CustomStack {
stack: Vec<i32>,
inc: Vec<i32>,
n: usize,
max_size: usize,
}

impl CustomStack {
fn new(max_size: i32) -> Self {
let max_size = max_size as usize;
let stack = vec![];
let inc = vec![0; (1 + max_size) as usize];
let n = 0;
CustomStack {
stack,
inc,
n,
max_size,
}
}

fn push(&mut self, x: i32) {
if self.n != self.max_size {
self.stack.push(x);
self.n += 1;
}
}

fn pop(&mut self) -> i32 {
if let Some(mut top) = self.stack.pop() {
self.inc[self.n - 1] += self.inc[self.n];
top += self.inc[self.n];
self.inc[self.n] = 0;
self.n -= 1;
top
} else {
-1
}
}

fn increment(&mut self, k: i32, val: i32) {
let k = k as usize;
if k > self.n {
self.inc[self.n] += val;
} else {
self.inc[k] += val;
}
}
}

#[test]
fn test() {
let mut stack = CustomStack::new(3);
stack.push(1);
stack.push(2);
assert_eq!(stack.pop(), 2);
stack.push(2);
stack.push(3);
stack.push(4);
stack.increment(5, 100);
stack.increment(2, 100);
assert_eq!(stack.pop(), 103);
assert_eq!(stack.pop(), 202);
assert_eq!(stack.pop(), 201);
assert_eq!(stack.pop(), -1);
}
``````