Leetcode
2020.05.05 16:44

225. Implement Stack using Queues

조회 수 408 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/



?

  1. 720. Longest Word in Dictionary

  2. 225. Implement Stack using Queues

  3. 56. Merge Intervals

  4. 844. Backspace String Compare

  5. 222. Count Complete Tree Nodes

  6. 697. Degree of an Array

  7. 605. Can Place Flowers

  8. 724. Find Pivot Index

  9. 448. Find All Numbers Disappeared in an Array

  10. 628. Maximum Product of Three Numbers

  11. 532. K-diff Pairs in an Array

  12. 897. Increasing Order Search Tree

  13. 872. Leaf-Similar Trees

  14. 876. Middle of the Linked List

  15. 203. Remove Linked List Elements

  16. 997. Find the Town Judge

  17. 270. Closest Binary Search Tree Value

  18. 687. Longest Univalue Path

  19. 783. Minimum Distance Between BST Nodes

  20. 235. Lowest Common Ancestor of a Binary Search Tree

Board Pagination Prev 1 2 3 4 Next
/ 4