(java)Implement Queue using Stacks
来源:互联网 发布:国外怎么在淘宝买东西 编辑:程序博客网 时间:2024/06/18 17:21
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.
- You must use only standard operations of a stack -- which means only
push to top
,peek/pop from top
,size
, andis 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).
思路:本题就是用栈实现队列操作,栈是先进后出,队列是先进先出,本题使用两个栈stack1,stack2来实现队列操作
对于push() 直接压人stack1中就行
对于pop()先要判断stack2中是否有元素,因为stack2是用来转置stack1的,如果stack2为空,进stack1中的元素转置入stack2,然后pop stack2
对于peek()也是跟pop一样的操作
代码如下,已通过leetcode
class MyQueue {
Stack<Integer> stack1=new Stack<Integer>();
Stack<Integer> stack2=new Stack<Integer>();
// Push element x to the back of queue.
public void push(int x) {
stack1.push(x);
}
// Removes the element from in front of queue.
public void pop() {
if(!stack2.empty()) {
stack2.pop();
return;
}
while(!stack1.empty()) {
stack2.push(stack1.pop());
}
stack2.pop();
}
// Get the front element.
public int peek() {
if(!stack2.empty()) {
return stack2.peek();
}
while(!stack1.empty()) {
stack2.push(stack1.pop());
}
return stack2.peek();
}
// Return whether the queue is empty.
public boolean empty() {
return stack1.empty()&&stack2.empty();
}
}
Stack<Integer> stack1=new Stack<Integer>();
Stack<Integer> stack2=new Stack<Integer>();
// Push element x to the back of queue.
public void push(int x) {
stack1.push(x);
}
// Removes the element from in front of queue.
public void pop() {
if(!stack2.empty()) {
stack2.pop();
return;
}
while(!stack1.empty()) {
stack2.push(stack1.pop());
}
stack2.pop();
}
// Get the front element.
public int peek() {
if(!stack2.empty()) {
return stack2.peek();
}
while(!stack1.empty()) {
stack2.push(stack1.pop());
}
return stack2.peek();
}
// Return whether the queue is empty.
public boolean empty() {
return stack1.empty()&&stack2.empty();
}
}
0 0
- (java)Implement Queue using Stacks
- Implement Queue using Stacks
- Implement Queue using Stacks
- Implement Queue using Stacks
- Implement Queue using Stacks
- Implement Queue using Stacks
- Implement Queue using Stacks
- Implement Queue using Stacks
- Implement Queue using Stacks
- Implement Queue using Stacks
- Implement Queue using Stacks
- Implement Queue using Stacks
- Implement Queue using Stacks
- Implement Queue using Stacks
- Implement Queue using Stacks
- Implement Queue using Stacks
- Implement Queue using Stacks
- Implement Queue using Stacks
- LeetCode Ugly Number || DP
- Socket中send函数的理解
- jQueryMobile快速入门
- C++重载,覆盖与隐藏
- JavaScript RegExp对象
- (java)Implement Queue using Stacks
- zabbix安装
- MTStatusBarOverlay —— 在状态栏上显示自定义的View
- 用Excel生成Ansys *VREAD函数所需的具有固定字符长度和小数位数的数据
- Service生命周期和启动方法以及IntentService
- 原生js跟jquery 的对比
- Using C++ With Objective-C
- QT QString 很全的使用
- Android OnLowMemory和OnTrimMemory