225.go

package p225

/**
Implement the following operations of a stack using queues.

push(x) -- Push element x onto stack.
pop() -- Removes the element on top of the stack.
top() -- Get the top element.
empty() -- Return whether the stack is empty.
Notes:
You must use only standard operations of a queue -- which means only push to back,
 peek/pop from front, size, and is empty operations are valid.

Depending on your language, queue may not be supported natively.
You may simulate a queue by using a list or deque (double-ended queue),
as long as you use only standard operations of a queue.
You may assume that all operations are valid
(for example, no pop or top operations will be called on an empty stack).
*/

type MyStack struct {
	q []int
}

/** Initialize your data structure here. */
func Constructor() MyStack {
	return MyStack{q: make([]int, 0)}
}

/** Push element x onto stack. */
func (this *MyStack) Push(x int) {
	this.q = append(this.q, x)
}

/** Removes the element on top of the stack and returns that element. */
func (this *MyStack) Pop() int {
	l := len(this.q)
	if l == 0 {
		return -1
	}
	f := this.q[l-1]
	this.q = this.q[:l-1]
	return f
}

/** Get the top element. */
func (this *MyStack) Top() int {
	l := len(this.q)
	if l == 0 {
		return -1
	}
	f := this.q[l-1]
	return f
}

/** Returns whether the stack is empty. */
func (this *MyStack) Empty() bool {
	return len(this.q) == 0
}

/**
 * Your MyStack object will be instantiated and called as such:
 * obj := Constructor();
 * obj.Push(x);
 * param_2 := obj.Pop();
 * param_3 := obj.Top();
 * param_4 := obj.Empty();
 */