{"id":456,"date":"2025-10-28T17:40:25","date_gmt":"2025-10-28T09:40:25","guid":{"rendered":"https:\/\/heyingnian.com\/?p=456"},"modified":"2025-10-28T17:41:53","modified_gmt":"2025-10-28T09:41:53","slug":"leetcode-236","status":"publish","type":"post","link":"https:\/\/heyingnian.com\/index.php\/2025\/10\/28\/leetcode-236\/","title":{"rendered":"\u4e8c\u53c9\u6811\u7684\u6700\u8fd1\u516c\u5171\u7956\u5148"},"content":{"rendered":"\n<h1 class=\"wp-block-heading\">\ud83d\udd17 \u4e8c\u53c9\u6811\u7684\u6700\u8fd1\u516c\u5171\u7956\u5148<\/h1>\n\n\n\n<p><strong>\u9898\u76ee\u6765\u6e90<\/strong>\uff1a<a target=\"_blank\" rel=\"noreferrer noopener\"><a href=\"https:\/\/leetcode.cn\/problems\/lowest-common-ancestor-of-a-binary-tree\/description\/?envType=study-plan-v2&amp;envId=top-100-liked\" target=\"_blank\" rel=\"noopener\">236. \u4e8c\u53c9\u6811\u7684\u6700\u8fd1\u516c\u5171\u7956\u5148 &#8211; \u529b\u6263\uff08LeetCode\uff09<\/a><\/a><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\ud83d\udccc \u9898\u76ee\u63cf\u8ff0<\/h2>\n\n\n\n<p>\u7ed9\u5b9a\u4e00\u4e2a\u4e8c\u53c9\u6811\uff0c\u627e\u5230\u8be5\u6811\u4e2d\u4e24\u4e2a\u6307\u5b9a\u8282\u70b9 <code>p<\/code> \u548c <code>q<\/code> \u7684<strong>\u6700\u8fd1\u516c\u5171\u7956\u5148<\/strong>\u3002<\/p>\n\n\n\n<p>\u6839\u636e\u767e\u5ea6\u767e\u79d1\u5b9a\u4e49\uff1a\u201c\u5bf9\u4e8e\u6709\u6839\u6811 T \u7684\u4e24\u4e2a\u8282\u70b9 p\u3001q\uff0c\u6700\u8fd1\u516c\u5171\u7956\u5148\u8868\u793a\u4e3a\u4e00\u4e2a\u8282\u70b9 x\uff0c\u6ee1\u8db3 x \u662f p\u3001q \u7684\u7956\u5148\u4e14 x \u7684\u6df1\u5ea6\u5c3d\u53ef\u80fd\u5927\uff08\u4e00\u4e2a\u8282\u70b9\u4e5f\u53ef\u4ee5\u662f\u5b83\u81ea\u5df1\u7684\u7956\u5148\uff09\u3002\u201d<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u2705 \u793a\u4f8b\u89e3\u6790<\/h2>\n\n\n\n<p><strong>\u793a\u4f8b 1\uff1a<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><div class='fancybox-wrapper lazyload-container-unload' data-fancybox='post-images' href='https:\/\/heyingnian.com\/wp-content\/uploads\/2025\/10\/image-13.png'><img class=\"lazyload lazyload-style-1\" src=\"data:image\/svg+xml;base64,PCEtLUFyZ29uTG9hZGluZy0tPgo8c3ZnIHdpZHRoPSIxIiBoZWlnaHQ9IjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgc3Ryb2tlPSIjZmZmZmZmMDAiPjxnPjwvZz4KPC9zdmc+\"  loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"190\" data-original=\"https:\/\/heyingnian.com\/wp-content\/uploads\/2025\/10\/image-13.png\" src=\"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB\/AAffA0nNPuCLAAAAAElFTkSuQmCC\" alt=\"\" class=\"wp-image-457\"  sizes=\"auto, (max-width: 200px) 100vw, 200px\" \/><\/div><\/figure>\n\n\n\n<pre class=\"wp-block-preformatted\"><code>\u8f93\u5165\uff1aroot = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 1<br>\u8f93\u51fa\uff1a3<br>\u89e3\u91ca\uff1a\u8282\u70b9 5 \u548c\u8282\u70b9 1 \u7684\u6700\u8fd1\u516c\u5171\u7956\u5148\u662f\u8282\u70b9 3\u3002<\/code><\/pre>\n\n\n\n<p><strong>\u793a\u4f8b 2\uff1a<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><div class='fancybox-wrapper lazyload-container-unload' data-fancybox='post-images' href='https:\/\/heyingnian.com\/wp-content\/uploads\/2025\/10\/image-14.png'><img class=\"lazyload lazyload-style-1\" src=\"data:image\/svg+xml;base64,PCEtLUFyZ29uTG9hZGluZy0tPgo8c3ZnIHdpZHRoPSIxIiBoZWlnaHQ9IjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgc3Ryb2tlPSIjZmZmZmZmMDAiPjxnPjwvZz4KPC9zdmc+\"  loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"190\" data-original=\"https:\/\/heyingnian.com\/wp-content\/uploads\/2025\/10\/image-14.png\" src=\"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB\/AAffA0nNPuCLAAAAAElFTkSuQmCC\" alt=\"\" class=\"wp-image-458\"  sizes=\"auto, (max-width: 200px) 100vw, 200px\" \/><\/div><\/figure>\n\n\n\n<pre class=\"wp-block-preformatted\"><code>\u8f93\u5165\uff1aroot = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 4<br>\u8f93\u51fa\uff1a5<br>\u89e3\u91ca\uff1a\u8282\u70b9 5 \u548c\u8282\u70b9 4 \u7684\u6700\u8fd1\u516c\u5171\u7956\u5148\u662f\u8282\u70b9 5\u3002\u56e0\u4e3a\u6839\u636e\u5b9a\u4e49\u6700\u8fd1\u516c\u5171\u7956\u5148\u8282\u70b9\u53ef\u4ee5\u4e3a\u8282\u70b9\u672c\u8eab\u3002<\/code><\/pre>\n\n\n\n<p><strong>\u793a\u4f8b 3\uff1a<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-preformatted\"><code>\u8f93\u5165\uff1aroot = [1,2], p = 1, q = 2<br>\u8f93\u51fa\uff1a1<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u26a0\ufe0f \u63d0\u793a<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u6811\u4e2d\u8282\u70b9\u6570\u76ee\u5728\u8303\u56f4\u00a0<code>[2, 10\u2075]<\/code>\u00a0\u5185<\/li>\n\n\n\n<li><code>-10\u2079 &lt;= Node.val &lt;= 10\u2079<\/code><\/li>\n\n\n\n<li>\u6240\u6709\u00a0<code>Node.val<\/code>\u00a0\u4e92\u4e0d\u76f8\u540c<\/li>\n\n\n\n<li><code>p != q<\/code><\/li>\n\n\n\n<li><code>p<\/code>\u00a0\u548c\u00a0<code>q<\/code>\u00a0\u5747\u5b58\u5728\u4e8e\u7ed9\u5b9a\u7684\u4e8c\u53c9\u6811\u4e2d<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\ud83d\udca1 \u89e3\u6cd5\uff1a\u9012\u5f52\u641c\u7d22 \u2014\u2014 O(n) \u65f6\u95f4\uff0cO(h) \u7a7a\u95f4<\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code>class Solution {\n    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {\n        \/\/ \u7ec8\u6b62\u6761\u4ef6\uff1a\n        \/\/ 1. \u5f53\u524d\u8282\u70b9\u4e3a\u7a7a\uff1b\n        \/\/ 2. \u5f53\u524d\u8282\u70b9\u4e3a p \u6216 q\u3002\n        if (root == null || root == p || root == q) {\n            return root;\n        }\n\n        \/\/ \u5728\u5de6\u5b50\u6811\u4e2d\u67e5\u627e p \u548c q \u7684\u6700\u8fd1\u516c\u5171\u7956\u5148\n        TreeNode left = lowestCommonAncestor(root.left, p, q);\n        \/\/ \u5728\u53f3\u5b50\u6811\u4e2d\u67e5\u627e p \u548c q \u7684\u6700\u8fd1\u516c\u5171\u7956\u5148\n        TreeNode right = lowestCommonAncestor(root.right, p, q);\n\n        \/\/ \u60c5\u51b5 1\uff1ap \u548c q \u5206\u522b\u4f4d\u4e8e\u5f53\u524d\u8282\u70b9\u7684\u5de6\u53f3\u5b50\u6811\u4e2d\uff0c\u5219\u5f53\u524d\u8282\u70b9\u5c31\u662f\u6700\u8fd1\u516c\u5171\u7956\u5148\n        if (left != null &amp;&amp; right != null) {\n            return root;\n        }\n        \/\/ \u60c5\u51b5 2\uff1ap \u548c q \u90fd\u4e0d\u5728\u5f53\u524d\u8282\u70b9\u7684\u53f3\u5b50\u6811\u4e2d\uff0c\u5219\u6700\u8fd1\u516c\u5171\u7956\u5148\u5728\u5de6\u5b50\u6811\u4e2d\n        if (left == null) {\n            return right;\n        }\n        \/\/ \u60c5\u51b5 3\uff1ap \u548c q \u90fd\u4e0d\u5728\u5f53\u524d\u8282\u70b9\u7684\u5de6\u5b50\u6811\u4e2d\uff0c\u5219\u6700\u8fd1\u516c\u5171\u7956\u5148\u5728\u53f3\u5b50\u6811\u4e2d\n        if (right == null) {\n            return left;\n        }\n        \n        \/\/ \u9ed8\u8ba4\u8fd4\u56de null\uff08\u5b9e\u9645\u4e0a\u4e0d\u4f1a\u5230\u8fbe\u8fd9\u91cc\uff09\n        return null;\n    }\n}<\/code><\/pre>\n\n\n\n<p>\u2705 <strong>\u5173\u952e\u70b9<\/strong>\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u9012\u5f52\u7ec8\u6b62\u6761\u4ef6<\/strong>\uff1a\u5f53\u8282\u70b9\u4e3a\u7a7a\u6216\u7b49\u4e8e\u00a0<code>p<\/code>\u00a0\u6216\u00a0<code>q<\/code>\u00a0\u65f6\u8fd4\u56de\u8be5\u8282\u70b9\uff1b<\/li>\n\n\n\n<li><strong>\u9012\u5f52\u5904\u7406<\/strong>\uff1a\u5206\u522b\u5bf9\u5de6\u53f3\u5b50\u6811\u8fdb\u884c\u9012\u5f52\u67e5\u627e\uff1b<\/li>\n\n\n\n<li><strong>\u5224\u65ad\u903b\u8f91<\/strong>\uff1a\u82e5\u5de6\u53f3\u5b50\u6811\u5747\u975e\u7a7a\uff0c\u5219\u5f53\u524d\u8282\u70b9\u5373\u4e3a\u6700\u8fd1\u516c\u5171\u7956\u5148\uff1b\u5426\u5219\uff0c\u8fd4\u56de\u975e\u7a7a\u5b50\u6811\u7684\u7ed3\u679c\u3002<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\ud83d\udcca \u590d\u6742\u5ea6\u5206\u6790<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u65f6\u95f4\u590d\u6742\u5ea6<\/strong>\uff1a<code>O(n)<\/code><br>\u6bcf\u4e2a\u8282\u70b9\u6700\u591a\u88ab\u8bbf\u95ee\u4e00\u6b21\uff0c\u6545\u65f6\u95f4\u590d\u6742\u5ea6\u4e3a <code>O(n)<\/code>\uff0c\u5176\u4e2d <code>n<\/code> \u662f\u6811\u4e2d\u8282\u70b9\u7684\u6570\u91cf\u3002<\/li>\n\n\n\n<li><strong>\u7a7a\u95f4\u590d\u6742\u5ea6<\/strong>\uff1a<code>O(h)<\/code><br>\u4e3b\u8981\u53d6\u51b3\u4e8e\u9012\u5f52\u8c03\u7528\u6808\u7684\u6df1\u5ea6\uff0c\u6700\u574f\u60c5\u51b5\u4e0b\uff08\u6811\u9000\u5316\u4e3a\u94fe\u8868\uff09\u4e3a <code>O(n)<\/code>\uff0c\u5e73\u5747\u60c5\u51b5\uff08\u5e73\u8861\u6811\uff09\u4e3a <code>O(log n)<\/code>\u3002<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\ud83e\udde9 \u89e3\u9898\u601d\u8def<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">\u6838\u5fc3\u601d\u60f3\uff1a\u5206\u6cbb\u7b56\u7565<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u9012\u5f52\u57fa\u7840<\/strong>\uff1a\u5982\u679c\u5f53\u524d\u8282\u70b9\u662f <code>null<\/code> \u6216\u8005\u6b63\u597d\u7b49\u4e8e <code>p<\/code> \u6216 <code>q<\/code>\uff0c\u5219\u76f4\u63a5\u8fd4\u56de\u5f53\u524d\u8282\u70b9\u3002<\/li>\n\n\n\n<li><strong>\u9012\u5f52\u8fc7\u7a0b<\/strong>\uff1a\u5bf9\u5f53\u524d\u8282\u70b9\u7684\u5de6\u53f3\u5b50\u6811\u5206\u522b\u8fdb\u884c\u9012\u5f52\u67e5\u627e\uff0c\u5bfb\u627e <code>p<\/code> \u548c <code>q<\/code> \u7684\u51fa\u73b0\u4f4d\u7f6e\u3002<\/li>\n\n\n\n<li><strong>\u5408\u5e76\u7ed3\u679c<\/strong>\uff1a\n<ul class=\"wp-block-list\">\n<li>\u5982\u679c\u00a0<code>p<\/code>\u00a0\u548c\u00a0<code>q<\/code>\u00a0\u5206\u522b\u51fa\u73b0\u5728\u5de6\u53f3\u5b50\u6811\u4e2d\uff0c\u5219\u5f53\u524d\u8282\u70b9\u5373\u4e3a\u5b83\u4eec\u7684\u6700\u8fd1\u516c\u5171\u7956\u5148\uff1b<\/li>\n\n\n\n<li>\u5982\u679c\u4e24\u8005\u90fd\u51fa\u73b0\u5728\u540c\u4e00\u4fa7\u5b50\u6811\u4e2d\uff0c\u5219\u6700\u8fd1\u516c\u5171\u7956\u5148\u4e5f\u5728\u8fd9\u4e00\u4fa7\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\">\u4e3a\u4ec0\u4e48\u8fd9\u79cd\u9012\u5f52\u65b9\u6cd5\u6709\u6548\uff1f<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u9012\u5f52\u672c\u8d28<\/strong>\uff1a\u5229\u7528\u4e86\u4e8c\u53c9\u6811\u7684\u5929\u7136\u9012\u5f52\u7ed3\u6784\uff0c\u4ece\u5e95\u90e8\u5411\u4e0a\u9010\u6b65\u786e\u5b9a\u6700\u8fd1\u516c\u5171\u7956\u5148\u3002<\/li>\n\n\n\n<li><strong>\u4f18\u5316\u6548\u7387<\/strong>\uff1a\u6bcf\u4e2a\u8282\u70b9\u4ec5\u8bbf\u95ee\u4e00\u6b21\uff0c\u907f\u514d\u91cd\u590d\u8ba1\u7b97\uff0c\u8fbe\u5230\u7ebf\u6027\u65f6\u95f4\u590d\u6742\u5ea6\u3002<\/li>\n\n\n\n<li><strong>\u7b80\u6d01\u5b9e\u73b0<\/strong>\uff1a\u901a\u8fc7\u7b80\u5355\u7684\u9012\u5f52\u4e0e\u6761\u4ef6\u5224\u65ad\u5373\u53ef\u89e3\u51b3\u95ee\u9898\uff0c\u4ee3\u7801\u76f4\u89c2\u6613\u61c2\u3002<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>\ud83d\udd17 \u4e8c\u53c9\u6811\u7684\u6700\u8fd1\u516c\u5171\u7956\u5148 \u9898\u76ee\u6765\u6e90\uff1a236. \u4e8c\u53c9\u6811\u7684\u6700\u8fd1\u516c\u5171\u7956\u5148 &#8211; \u529b\u6263\uff08LeetCode\uff09  [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[39,12],"tags":[57,58,14],"class_list":["post-456","post","type-post","status-publish","format-standard","hentry","category-binary_tree","category-algorithm","tag-binary_tree","tag-dfs","tag-algorithm"],"_links":{"self":[{"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/posts\/456","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/comments?post=456"}],"version-history":[{"count":1,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/posts\/456\/revisions"}],"predecessor-version":[{"id":459,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/posts\/456\/revisions\/459"}],"wp:attachment":[{"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/media?parent=456"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/categories?post=456"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/tags?post=456"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}