232 利用 container/list.List 重新实现了代码。close #37

Author: aQuaYi

Algorithms/0232.implement-queue-using-stacks/README.md

@@ -4,25 +4,25 @@
 
 Implement the following operations of a queue using stacks.
 
+- push(x) -- Push element x to the back of queue.
+- pop() -- Removes the element from in front of queue.
+- peek() -- Get the front element.
+- empty() -- Return whether the queue is empty.
 
-push(x) -- Push element x to the back of queue.
+Example:
 
+```text
+MyQueue queue = new MyQueue();
 
-pop() -- Removes the element from in front of queue.
-
-
-peek() -- Get the front element.
-
-
-empty() -- Return whether the queue is empty.
-
+queue.push(1);
+queue.push(2);
+queue.peek();  // returns 1
+queue.pop();   // returns 1
+queue.empty(); // returns false
+```
 
 Notes:
 
-You must use only standard operations of a stack -- which means only push to top, peek/pop from top, size, and is empty operations are valid.
-Depending on your language, stack may not be supported natively. You may simulate a stack by using a list or deque (double-ended queue), as long as you use only standard operations of a stack.
-You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue).
-
-## 解题思路
-
-见程序注释
+- You must use only standard operations of a stack -- which means only push to top, peek/pop from top, size, and is empty operations are valid.
+- Depending on your language, stack may not be supported natively. You may simulate a stack by using a list or deque (double-ended queue), as long as you use only standard operations of a stack.
+- You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue).

Algorithms/0232.implement-queue-using-stacks/implement-queue-using-stacks.go

@@ -1,80 +1,40 @@
 package problem0232
 
-// MyQueue 是利用 栈 实现的队列
+import "container/list"
+
+// MyQueue 是利用 list 实现的队列
 type MyQueue struct {
-	a, b *Stack
+	list *list.List
 }
 
 // Constructor Initialize your data structure here.
 func Constructor() MyQueue {
-	return MyQueue{a: NewStack(), b: NewStack()}
+	return MyQueue{
+		list: list.New(),
+	}
 }
 
 // Push element x to the back of queue.
-func (mq *MyQueue) Push(x int) {
-	mq.a.Push(x)
+func (q *MyQueue) Push(x int) {
+	q.list.PushBack(x)
 }
 
 // Pop Removes the element from in front of queue and returns that element.
-func (mq *MyQueue) Pop() int {
-	if mq.b.Len() == 0 {
-		for mq.a.Len() > 0 {
-			mq.b.Push(mq.a.Pop())
-		}
-	}
-
-	return mq.b.Pop()
+func (q *MyQueue) Pop() int {
+	front := q.list.Front()
+	res := front.Value.(int)
+	q.list.Remove(front)
+	return res
 }
 
 // Peek Get the front element.
-func (mq *MyQueue) Peek() int {
-	res := mq.Pop()
-	mq.b.Push(res)
+func (q *MyQueue) Peek() int {
+	front := q.list.Front()
+	res := front.Value.(int)
 	return res
 }
 
 // Empty returns whether the queue is empty.
-func (mq *MyQueue) Empty() bool {
-	return mq.a.Len() == 0 && mq.b.Len() == 0
-}
-
-/**
- * Your MyQueue object will be instantiated and called as such:
- * obj := Constructor();
- * obj.Push(x);
- * param_2 := obj.Pop();
- * param_3 := obj.Peek();
- * param_4 := obj.Empty();
- */
-
-// Stack 是用于存放 int 的 栈
-type Stack struct {
-	nums []int
-}
-
-// NewStack 返回 *kit.Stack
-func NewStack() *Stack {
-	return &Stack{nums: []int{}}
-}
-
-// Push 把 n 放入 栈
-func (s *Stack) Push(n int) {
-	s.nums = append(s.nums, n)
-}
-
-// Pop 从 s 中取出最后放入 栈 的值
-func (s *Stack) Pop() int {
-	res := s.nums[len(s.nums)-1]
-	s.nums = s.nums[:len(s.nums)-1]
-	return res
-}
-
-// Len 返回 s 的长度
-func (s *Stack) Len() int {
-	return len(s.nums)
-}
-
-// IsEmpty 反馈 s 是否为空
-func (s *Stack) IsEmpty() bool {
-	return s.Len() == 0
+func (q *MyQueue) Empty() bool {
+	return q.list.Len() == 0
 }

Algorithms/0232.implement-queue-using-stacks/implement-queue-using-stacks_test.go

@@ -16,31 +16,10 @@ func Test_MyQueue(t *testing.T) {
 
 	for i := start; i < end; i++ {
 		q.Push(i)
-		ast.Equal(start , q.Peek(), "查看 q.Peek()")
+		ast.Equal(start, q.Peek(), "查看 q.Peek()")
 	}
 
 	for i := start; i < end; i++ {
 		ast.Equal(i, q.Pop(), "从 q 中 pop 出数来。")
 	}
-
-	ast.True(q.Empty(), "检查 Pop 完毕后的 q 是否为空")
-}
-func Test_Stack(t *testing.T) {
-	ast := assert.New(t)
-
-	s := NewStack()
-	ast.True(s.IsEmpty(), "检查新建的 s 是否为空")
-
-	start, end := 0, 100
-
-	for i := start; i < end; i++ {
-		s.Push(i)
-		ast.Equal(i-start+1, s.Len(), "Push 后检查 q 的长度。")
-	}
-
-	for i := end - 1; i >= start; i-- {
-		ast.Equal(i, s.Pop(), "从 s 中 pop 出数来。")
-	}
-
-	ast.True(s.IsEmpty(), "检查 Pop 完毕后的 s 是否为空")
 }