1381. Design a stack with increment operation

//1381. Design a stack with increment operation

class CustomStack {
    private int[] stackArray;
    private int[] incrementArray;
    private int topIndex;

    public CustomStack(int maxSize) {
        stackArray = new int[maxSize];
        incrementArray = new int[maxSize];
        topIndex = -1;
    }
    
    public void push(int x) {
        if(topIndex < stackArray.length - 1) {
            stackArray[++topIndex] = x;
        }
    }
    
    public int pop() {
        if(topIndex < 0) {
            return -1;
        }

        int result = stackArray[topIndex] + incrementArray[topIndex];

        if(topIndex > 0) {
            incrementArray[topIndex - 1] += incrementArray[topIndex];
        }

        incrementArray[topIndex] = 0;
        topIndex--;

        return result;
    }
    
    public void increment(int k, int val) {
        if(topIndex >= 0) {
            int incrementIndex = Math.min(topIndex, k - 1);
            
            incrementArray[incrementIndex] += val;
        }
    }
}