package _155_min_stack

// 155. 最小栈
// https://leetcode-cn.com/problems/min-stack/

type MinStack struct {
	s      []int
	preMin []int
}

func Constructor() MinStack {
	return MinStack{
		s:      []int{},
		preMin: []int{},
	}
}

func (this *MinStack) Push(val int) {

	if len(this.s) == 0 {
		this.preMin = append(this.preMin, val)
	} else {
		if this.preMin[len(this.s)-1] > val {
			this.preMin = append(this.preMin, val)
		} else {
			this.preMin = append(this.preMin, this.preMin[len(this.s)-1])
		}
	}
	this.s = append(this.s, val)

}

func (this *MinStack) Pop() {
	if len(this.s) == 0 {
		return
	}
	l := len(this.s)
	this.s = this.s[:l-1]
	this.preMin = this.preMin[:l-1]
}

func (this *MinStack) Top() int {
	if len(this.s) == 0 {
		return 0
	}
	return this.s[len(this.s)-1]
}

func (this *MinStack) GetMin() int {
	if len(this.s) == 0 {
		return 0
	}
	return this.preMin[len(this.s)-1]
}

/**
 * Your MinStack object will be instantiated and called as such:
 * obj := Constructor();
 * obj.Push(val);
 * obj.Pop();
 * param_3 := obj.Top();
 * param_4 := obj.GetMin();
 */