125 lines
14 KiB
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125 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-add-two-numbers-ii · MarkDown</title><meta name="description" content="leetcode-add-two-numbers-ii - 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"><style><!-- hexo-inject:begin --><!-- hexo-inject:end -->mjx-container[jax="SVG"] {
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</style><!-- hexo-inject:begin --><!-- hexo-inject:end --></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="https://bearmiebear.blogspot.com" target="_blank" class="nav-list-link">BEAR</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-add-two-numbers-ii</h1><div class="post-meta"><div class="post-time">2020年4月14日</div></div><div class="post-content"><h3 id="445-__u4E24_u6570_u76F8_u52A0_II"><a href="#445-__u4E24_u6570_u76F8_u52A0_II" class="headerlink" title="445. 两数相加 II"></a>445. 两数相加 II</h3><p><a href="https://leetcode-cn.com/problems/add-two-numbers-ii/" target="_blank" rel="noopener">题目</a></p>
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<p>看到顺序的链表就想到用倒序链表的方法做，折腾了半天</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><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">ListNode</span>:</span></span><br><span class="line"> <span class="function"><span class="keyword">def</span> <span class="title">__init__</span><span class="params">(self, x)</span>:</span></span><br><span class="line"> self.val = x</span><br><span class="line"> self.next = <span class="keyword">None</span></span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span>:</span></span><br><span class="line"> <span class="function"><span class="keyword">def</span> <span class="title">addTwoNumbers</span><span class="params">(self, l1: ListNode, l2: ListNode)</span> -> ListNode:</span></span><br><span class="line"> <span class="function"><span class="keyword">def</span> <span class="title">_reverse</span><span class="params">(l)</span>:</span></span><br><span class="line"> <span class="keyword">if</span> l.next:</span><br><span class="line"> last = _reverse(l.next)</span><br><span class="line"> l.next.next = l</span><br><span class="line"> l.next = <span class="keyword">None</span></span><br><span class="line"> <span class="keyword">return</span> last</span><br><span class="line"> <span class="keyword">return</span> l</span><br><span class="line"></span><br><span class="line"> l1e = _reverse(l1)</span><br><span class="line"> l2e = _reverse(l2)</span><br><span class="line"> new_l = ListNode(<span class="number">0</span>)</span><br><span class="line"> head = new_l</span><br><span class="line"> c = <span class="number">0</span></span><br><span class="line"> <span class="keyword">import</span> ipdb; ipdb.set_trace()</span><br><span class="line"> <span class="keyword">while</span> l1e <span class="keyword">and</span> l2e:</span><br><span class="line"> new_val = l1e.val + l2e.val</span><br><span class="line"> <span class="keyword">if</span> c==<span class="number">1</span>:</span><br><span class="line"> new_val += <span class="number">1</span></span><br><span class="line"> c = <span class="number">0</span></span><br><span class="line"> <span class="keyword">if</span> new_val >= <span class="number">10</span>:</span><br><span class="line"> new_val -= <span class="number">10</span></span><br><span class="line"> c = <span class="number">1</span></span><br><span class="line"></span><br><span class="line"> new_l.val = new_val</span><br><span class="line"> next_n = <span class="keyword">None</span></span><br><span class="line"> <span class="keyword">if</span> l1e.next <span class="keyword">and</span> l2e.next <span class="keyword">or</span> c:</span><br><span class="line"> next_n = ListNode(c)</span><br><span class="line"> new_l.next = next_n</span><br><span class="line"> new_l = next_n</span><br><span class="line"> l1e = l1e.next</span><br><span class="line"> l2e = l2e.next</span><br><span class="line"> <span class="keyword">if</span> l2e:</span><br><span class="line"> l1e = l2e</span><br><span class="line"> <span class="keyword">if</span> <span class="keyword">not</span> l1e <span class="keyword">and</span> c:</span><br><span class="line"> l1e = ListNode(<span class="number">0</span>)</span><br><span class="line"> <span class="keyword">while</span> l1e:</span><br><span class="line"> new_l.val = l1e.val</span><br><span class="line"> new_l.val += c</span><br><span class="line"> c = <span class="number">0</span></span><br><span class="line"> <span class="keyword">if</span> new_l.val >= <span class="number">10</span>:</span><br><span class="line"> c = <span class="number">1</span></span><br><span class="line"> new_l.val -= <span class="number">10</span></span><br><span class="line"> l1e = l1e.next</span><br><span class="line"> <span class="keyword">if</span> l1e:</span><br><span class="line"> new_l.next = ListNode(<span class="number">0</span>)</span><br><span class="line"> new_l = new_l.next</span><br><span class="line"> <span class="keyword">else</span>:</span><br><span class="line"> new_l.next = ListNode(<span class="number">1</span>)</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> _reverse(head)</span><br><span class="line"></span><br><span class="line"> <span class="comment"># 84 ms 13.9 MB</span></span><br></pre></td></tr></table></figure>
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<p>最后面各种进位的处理应该还可以更清晰优雅一些，但是懒得搞了，感觉很蠢。翻了答案看到了小 tips，需要倒序处理的情况可以用栈。</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></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span>:</span></span><br><span class="line"> <span class="function"><span class="keyword">def</span> <span class="title">addTwoNumbers</span><span class="params">(self, l1: ListNode, l2: ListNode)</span> -> ListNode:</span></span><br><span class="line"> s1, s2 = [], []</span><br><span class="line"> <span class="keyword">while</span> l1:</span><br><span class="line"> s1.append(l1.val)</span><br><span class="line"> l1 = l1.next</span><br><span class="line"> <span class="keyword">while</span> l2:</span><br><span class="line"> s2.append(l2.val)</span><br><span class="line"> l2 = l2.next</span><br><span class="line"> ans = <span class="keyword">None</span></span><br><span class="line"> carry = <span class="number">0</span></span><br><span class="line"> <span class="keyword">while</span> s1 <span class="keyword">or</span> s2 <span class="keyword">or</span> carry != <span class="number">0</span>:</span><br><span class="line"> a = <span class="number">0</span> <span class="keyword">if</span> <span class="keyword">not</span> s1 <span class="keyword">else</span> s1.pop()</span><br><span class="line"> b = <span class="number">0</span> <span class="keyword">if</span> <span class="keyword">not</span> s2 <span class="keyword">else</span> s2.pop()</span><br><span class="line"> cur = a + b + carry</span><br><span class="line"> carry = cur // <span class="number">10</span></span><br><span class="line"> cur %= <span class="number">10</span></span><br><span class="line"> curnode = ListNode(cur)</span><br><span class="line"> curnode.next = ans</span><br><span class="line"> ans = curnode</span><br><span class="line"> <span class="keyword">return</span> ans</span><br><span class="line"></span><br><span class="line">作者：LeetCode-Solution</span><br><span class="line">链接：https://leetcode-cn.com/problems/add-two-numbers-ii/solution/liang-shu-xiang-jia-ii-by-leetcode-solution/</span><br><span class="line">来源：力扣（LeetCode）</span><br><span class="line">著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。</span><br></pre></td></tr></table></figure>
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<p>不过就执行效率来看差不多。</p>
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