minStack.ts

class MinStack {
    #stack = [];
    #history = [Number.POSITIVE_INFINITY];
    constructor() {}

    push(val: number): void {
        this.#stack.push(val);
        if (val <= this.#history[this.#history.length - 1]) {
            this.#history.push(val);
        }
    }

    pop(): void {
        const popped = this.#stack.pop();
        if (popped === this.#history[this.#history.length - 1]) {
            this.#history.pop();
        }
    }

    top(): number {
        return this.#stack[this.#stack.length - 1];
    }

    getMin(): number {
        return this.#history[this.#history.length - 1];
    }
}

/**
 * Your MinStack object will be instantiated and called as such:
 * var obj = new MinStack()
 * obj.push(val)
 * obj.pop()
 * var param_3 = obj.top()
 * var param_4 = obj.getMin()
 */