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10 lines
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<!DOCTYPE html><html lang="zh-CN"><head><meta charset="utf-8"><meta name="X-UA-Compatible" content="IE=edge"><title> leetcode-225 · MarkDown</title><meta name="description" content="leetcode-225 - Ching"><meta name="viewport" content="width=device-width, initial-scale=1"><link rel="short icon" href="/favicon.png"><link rel="stylesheet" href="/css/apollo.css"><link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Source+Sans+Pro:400,600" type="text/css"><meta name="generator" content="Hexo 6.0.0"><link rel="alternate" href="/atom.xml" title="MarkDown" type="application/atom+xml">
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</head><body><header><a href="/" class="logo-link"><img src="/logo.png"></a><ul class="nav nav-list"><li class="nav-list-item"><a href="/" target="_self" class="nav-list-link">ALL</a></li><li class="nav-list-item"><a href="/categories/leetcode/" target="_self" class="nav-list-link">LEETCODE</a></li><li class="nav-list-item"><a href="/atom.xml" target="_self" class="nav-list-link">RSS</a></li></ul></header><section class="container"><div class="post"><article class="post-block"><h1 class="post-title">leetcode-225</h1><div class="post-meta"><div class="post-time">2020年3月23日</div></div><div class="post-content"><h3 id="225-用队列实现栈"><a href="#225-用队列实现栈" class="headerlink" title="225. 用队列实现栈"></a>225. 用队列实现栈</h3><p><a target="_blank" rel="noopener" href="https://leetcode-cn.com/problems/implement-stack-using-queues/">题目</a></p>
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<p>注意栈是 FILO(First In Last Out)，Python 的 list 是 FIFO(First In First Out)。</p>
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<figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">MyStack</span>:</span></span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">def</span> <span class="title">__init__</span>(<span class="params">self</span>):</span></span><br><span class="line"> <span class="string">"""</span></span><br><span class="line"><span class="string"> Initialize your data structure here.</span></span><br><span class="line"><span class="string"> """</span></span><br><span class="line"> self.data = []</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">def</span> <span class="title">push</span>(<span class="params">self, x: <span class="built_in">int</span></span>) -> <span class="literal">None</span>:</span></span><br><span class="line"> <span class="string">"""</span></span><br><span class="line"><span class="string"> Push element x onto stack.</span></span><br><span class="line"><span class="string"> """</span></span><br><span class="line"> self.data.append(x)</span><br><span class="line"> <span class="keyword">return</span></span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">def</span> <span class="title">pop</span>(<span class="params">self</span>) -> <span class="built_in">int</span>:</span></span><br><span class="line"> <span class="string">"""</span></span><br><span class="line"><span class="string"> Removes the element on top of the stack and returns that element.</span></span><br><span class="line"><span class="string"> """</span></span><br><span class="line"> <span class="keyword">return</span> self.data.pop(-<span class="number">1</span>)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">def</span> <span class="title">top</span>(<span class="params">self</span>) -> <span class="built_in">int</span>:</span></span><br><span class="line"> <span class="string">"""</span></span><br><span class="line"><span class="string"> Get the top element.</span></span><br><span class="line"><span class="string"> """</span></span><br><span class="line"> <span class="keyword">return</span> self.data[-<span class="number">1</span>]</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">def</span> <span class="title">empty</span>(<span class="params">self</span>) -> <span class="built_in">bool</span>:</span></span><br><span class="line"> <span class="string">"""</span></span><br><span class="line"><span class="string"> Returns whether the stack is empty.</span></span><br><span class="line"><span class="string"> """</span></span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">not</span> <span class="built_in">bool</span>(self.data)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line"><span class="comment"># Your MyStack object will be instantiated and called as such:</span></span><br><span class="line"><span class="comment"># obj = MyStack()</span></span><br><span class="line"><span class="comment"># obj.push(x)</span></span><br><span class="line"><span class="comment"># param_2 = obj.pop()</span></span><br><span class="line"><span class="comment"># param_3 = obj.top()</span></span><br><span class="line"><span class="comment"># param_4 = obj.empty()</span></span><br><span class="line"></span><br><span class="line"><span class="comment">#24 ms 13.5 MB</span></span><br></pre></td></tr></table></figure>
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