Leetcode
2020.05.05 16:44

225. Implement Stack using Queues

조회 수 62 추천 수 0 댓글 0
?

단축키

Prev이전 문서

Next다음 문서

크게 작게 위로 아래로 댓글로 가기 인쇄
?

단축키

Prev이전 문서

Next다음 문서

크게 작게 위로 아래로 댓글로 가기 인쇄

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.

Example:

MyStack stack = new MyStack();

stack.push(1);
stack.push(2);  
stack.top();   // returns 2
stack.pop();   // returns 2
stack.empty(); // returns false

Notes:

  • You must use only standard operations of a queue -- which means only push to backpeek/pop from frontsize, 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).


class MyStack {
    List<Integer> list;

    /** Initialize your data structure here. */
    public MyStack() {
        list = new ArrayList<>();
    }
    
    /** Push element x onto stack. */
    public void push(int x) {
        list.add(x);
    }
    
    /** Removes the element on top of the stack and returns that element. */
    public int pop() {
        return list.remove(list.size()-1);
    }
    
    /** Get the top element. */
    public int top() {
        return list.get(list.size()-1);
    }
    
    /** Returns whether the stack is empty. */
    public boolean empty() {
        return list.size() == 0;
    }
}

/**
 * Your MyStack object will be instantiated and called as such:
 * MyStack obj = new MyStack();
 * obj.push(x);
 * int param_2 = obj.pop();
 * int param_3 = obj.top();
 * boolean param_4 = obj.empty();
 */

[문제] https://leetcode.com/problems/implement-stack-using-queues/



?

List of Articles
번호 분류 제목 글쓴이 날짜 조회 수
77 Leetcode 720. Longest Word in Dictionary hooni 2020.05.07 58
» Leetcode 225. Implement Stack using Queues hooni 2020.05.05 62
75 Leetcode 56. Merge Intervals hooni 2020.05.05 52
74 Leetcode 844. Backspace String Compare hooni 2020.05.05 52
73 Leetcode 222. Count Complete Tree Nodes hooni 2020.05.05 55
72 Leetcode 697. Degree of an Array hooni 2020.05.05 45
71 Leetcode 605. Can Place Flowers hooni 2020.05.05 49
70 Leetcode 724. Find Pivot Index hooni 2020.05.05 48
69 Leetcode 448. Find All Numbers Disappeared in an Array hooni 2020.05.05 38
68 Leetcode 628. Maximum Product of Three Numbers hooni 2020.05.05 36
67 Leetcode 532. K-diff Pairs in an Array hooni 2020.05.04 35
66 Leetcode 897. Increasing Order Search Tree hooni 2020.05.04 21
65 Leetcode 872. Leaf-Similar Trees file hooni 2020.05.04 27
64 Leetcode 876. Middle of the Linked List hooni 2020.05.04 29
63 Leetcode 203. Remove Linked List Elements hooni 2020.05.04 30
62 Leetcode 997. Find the Town Judge hooni 2020.05.02 38
61 Leetcode 270. Closest Binary Search Tree Value hooni 2020.05.01 29
60 Leetcode 687. Longest Univalue Path hooni 2020.05.01 30
59 Leetcode 783. Minimum Distance Between BST Nodes hooni 2020.05.01 40
58 Leetcode 235. Lowest Common Ancestor of a Binary Search Tree file hooni 2020.05.01 47
Board Pagination Prev 1 2 3 4 Next
/ 4