{"id":438,"date":"2025-10-20T19:32:10","date_gmt":"2025-10-20T11:32:10","guid":{"rendered":"https:\/\/heyingnian.com\/?p=438"},"modified":"2025-10-20T19:35:19","modified_gmt":"2025-10-20T11:35:19","slug":"leetcode-199","status":"publish","type":"post","link":"https:\/\/heyingnian.com\/index.php\/2025\/10\/20\/leetcode-199\/","title":{"rendered":"\u4e8c\u53c9\u6811\u7684\u53f3\u89c6\u56fe"},"content":{"rendered":"\n<h1 class=\"wp-block-heading\">\ud83d\udd17 \u4e8c\u53c9\u6811\u7684\u53f3\u89c6\u56fe<\/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\/binary-tree-right-side-view\/description\/?envType=study-plan-v2&amp;envId=top-100-liked\" target=\"_blank\" rel=\"noopener\">199. \u4e8c\u53c9\u6811\u7684\u53f3\u89c6\u56fe &#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\u7684\u6839\u8282\u70b9 <code>root<\/code>\uff0c\u60f3\u8c61\u81ea\u5df1\u7ad9\u5728\u5b83\u7684<strong>\u53f3\u4fa7<\/strong>\uff0c\u6309\u7167\u4ece<strong>\u9876\u90e8\u5230\u5e95\u90e8<\/strong>\u7684\u987a\u5e8f\uff0c\u8fd4\u56de\u4ece\u53f3\u4fa7\u6240\u80fd\u770b\u5230\u7684\u8282\u70b9\u503c\u3002<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>\u5373\uff1a\u4ece\u53f3\u5f80\u5de6\u770b\u65f6\uff0c\u6bcf\u5c42\u53ea\u80fd\u770b\u5230<strong>\u6700\u53f3\u8fb9\u7684\u90a3\u4e2a\u8282\u70b9<\/strong>\u3002<\/p>\n<\/blockquote>\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<pre class=\"wp-block-preformatted\"><code>\u8f93\u5165\uff1aroot = [1,2,3,null,5,null,4]<br>\u8f93\u51fa\uff1a[1,3,4]<\/code><\/pre>\n\n\n\n<p>\u89e3\u91ca\uff1a<\/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-8.png'><img class=\"lazyload lazyload-style-1\" src=\"data:image\/svg+xml;base64,PCEtLUFyZ29uTG9hZGluZy0tPgo8c3ZnIHdpZHRoPSIxIiBoZWlnaHQ9IjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgc3Ryb2tlPSIjZmZmZmZmMDAiPjxnPjwvZz4KPC9zdmc+\"  loading=\"lazy\" decoding=\"async\" width=\"671\" height=\"348\" data-original=\"https:\/\/heyingnian.com\/wp-content\/uploads\/2025\/10\/image-8.png\" src=\"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB\/AAffA0nNPuCLAAAAAElFTkSuQmCC\" alt=\"\" class=\"wp-image-443\"  sizes=\"auto, (max-width: 671px) 100vw, 671px\" \/><\/div><\/figure>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7b2c 0 \u5c42\uff1a<code>[1]<\/code>\u00a0\u2192 \u53f3\u4fa7\u770b\u5230\u00a0<code>1<\/code><\/li>\n\n\n\n<li>\u7b2c 1 \u5c42\uff1a<code>[2,3]<\/code>\u00a0\u2192 \u53f3\u4fa7\u770b\u5230\u00a0<code>3<\/code><\/li>\n\n\n\n<li>\u7b2c 2 \u5c42\uff1a<code>[5,4]<\/code>\u00a0\u2192 \u53f3\u4fa7\u770b\u5230\u00a0<code>4<\/code><\/li>\n<\/ul>\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-9.png'><img class=\"lazyload lazyload-style-1\" src=\"data:image\/svg+xml;base64,PCEtLUFyZ29uTG9hZGluZy0tPgo8c3ZnIHdpZHRoPSIxIiBoZWlnaHQ9IjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgc3Ryb2tlPSIjZmZmZmZmMDAiPjxnPjwvZz4KPC9zdmc+\"  loading=\"lazy\" decoding=\"async\" width=\"829\" height=\"443\" data-original=\"https:\/\/heyingnian.com\/wp-content\/uploads\/2025\/10\/image-9.png\" src=\"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB\/AAffA0nNPuCLAAAAAElFTkSuQmCC\" alt=\"\" class=\"wp-image-444\"  sizes=\"auto, (max-width: 829px) 100vw, 829px\" \/><\/div><\/figure>\n\n\n\n<pre class=\"wp-block-preformatted\"><code>\u8f93\u5165\uff1aroot = [1,2,3,4,null,null,null,5]<br>\u8f93\u51fa\uff1a[1,3,4,5]<\/code><\/pre>\n\n\n\n<p>\u89e3\u91ca\uff1a<br>\u6811\u5411\u5de6\u503e\u659c\u5f88\u6df1\uff0c\u4f46\u6bcf\u5c42\u6700\u53f3\u8282\u70b9\u4f9d\u6b21\u4e3a <code>1 \u2192 3 \u2192 4 \u2192 5<\/code>\u3002<\/p>\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,null,3]<br>\u8f93\u51fa\uff1a[1,3]<\/code><\/pre>\n\n\n\n<p><strong>\u793a\u4f8b 4\uff1a<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-preformatted\"><code>\u8f93\u5165\uff1aroot = []<br>\u8f93\u51fa\uff1a[]<\/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>[0, 100]<\/code>\u00a0\u5185<\/li>\n\n\n\n<li><code>-100 &lt;= Node.val &lt;= 100<\/code><\/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\u5c42\u5e8f\u904d\u5386\uff08BFS\uff09\u2014\u2014 O(n) \u65f6\u95f4\uff0cO(w) \u7a7a\u95f4<\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code>class Solution {\n    public List&lt;Integer> rightSideView(TreeNode root) {\n        List&lt;Integer> result = new ArrayList&lt;>();\n        if (root == null) {\n            return result;\n        }\n\n        Queue&lt;TreeNode> queue = new LinkedList&lt;>();\n        queue.offer(root);\n\n        while (!queue.isEmpty()) {\n            int levelSize = queue.size(); \/\/ \u5f53\u524d\u5c42\u7684\u8282\u70b9\u6570\n\n            for (int i = 0; i &lt; levelSize; i++) {\n                TreeNode node = queue.poll();\n\n                \/\/ \u5982\u679c\u662f\u5f53\u524d\u5c42\u7684\u6700\u540e\u4e00\u4e2a\u8282\u70b9\uff0c\u52a0\u5165\u7ed3\u679c\n                if (i == levelSize - 1) {\n                    result.add(node.val);\n                }\n\n                \/\/ \u5c06\u4e0b\u4e00\u5c42\u8282\u70b9\u52a0\u5165\u961f\u5217\uff08\u5148\u5de6\u540e\u53f3\uff0c\u4fdd\u8bc1\u987a\u5e8f\uff09\n                if (node.left != null) {\n                    queue.offer(node.left);\n                }\n                if (node.right != null) {\n                    queue.offer(node.right);\n                }\n            }\n        }\n\n        return result;\n    }\n}<\/code><\/pre>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>\u2705 <strong>\u5173\u952e\u70b9<\/strong>\uff1a\u6bcf\u5c42\u904d\u5386\u65f6\uff0c<strong>\u53ea\u53d6\u6700\u540e\u4e00\u4e2a\u51fa\u961f\u7684\u8282\u70b9<\/strong>\uff0c\u5373\u4e3a\u8be5\u5c42\u6700\u53f3\u4fa7\u53ef\u89c1\u8282\u70b9\u3002<\/p>\n<\/blockquote>\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\u6070\u597d\u88ab\u8bbf\u95ee\u4e00\u6b21\uff0c\u603b\u5171\u6709 <code>n<\/code> \u4e2a\u8282\u70b9\u3002<\/li>\n\n\n\n<li><strong>\u7a7a\u95f4\u590d\u6742\u5ea6<\/strong>\uff1a<code>O(w)<\/code><br><code>w<\/code> \u662f\u4e8c\u53c9\u6811\u7684\u6700\u5927\u5bbd\u5ea6\uff08\u5373\u67d0\u4e00\u5c42\u6700\u591a\u8282\u70b9\u6570\uff09\u3002\n<ul class=\"wp-block-list\">\n<li>\u6700\u574f\u60c5\u51b5\uff08\u5b8c\u5168\u4e8c\u53c9\u6811\u5e95\u5c42\uff09\uff1a<code>w \u2248 n\/2<\/code>\u00a0\u2192\u00a0<code>O(n)<\/code><\/li>\n\n\n\n<li>\u6700\u597d\u60c5\u51b5\uff08\u94fe\u8868\uff09\uff1a<code>w = 1<\/code>\u00a0\u2192\u00a0<code>O(1)<\/code><\/li>\n<\/ul>\n<\/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\">\u4e3a\u4ec0\u4e48\u7528 BFS\uff08\u5c42\u5e8f\u904d\u5386\uff09\uff1f<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u201c\u53f3\u89c6\u56fe\u201d\u672c\u8d28\u4e0a\u662f<strong>\u6309\u5c42\u53d6\u6700\u53f3\u8282\u70b9<\/strong>\uff0c\u5929\u7136\u5951\u5408<strong>\u6309\u5c42\u5904\u7406<\/strong>\u7684 BFS\u3002<\/li>\n\n\n\n<li>DFS \u4e5f\u53ef\u5b9e\u73b0\uff08\u8bb0\u5f55\u6df1\u5ea6\uff0c\u53ea\u4fdd\u7559\u6bcf\u5c42\u7b2c\u4e00\u6b21\u8bbf\u95ee\u7684\u53f3\u8282\u70b9\uff09\uff0c\u4f46 BFS \u66f4\u76f4\u89c2\u3002<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">\u7b97\u6cd5\u6b65\u9aa4\uff1a<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li>\u521d\u59cb\u5316\u961f\u5217\uff0c\u5c06\u6839\u8282\u70b9\u5165\u961f\u3002<\/li>\n\n\n\n<li>\u5f53\u961f\u5217\u975e\u7a7a\u65f6\uff0c\u5904\u7406\u5f53\u524d\u6574\u5c42\uff1a\n<ul class=\"wp-block-list\">\n<li>\u8bb0\u5f55\u5f53\u524d\u5c42\u8282\u70b9\u6570\u00a0<code>size<\/code>\u3002<\/li>\n\n\n\n<li>\u904d\u5386\u00a0<code>size<\/code>\u00a0\u6b21\uff0c\u4f9d\u6b21\u51fa\u961f\uff1a\n<ul class=\"wp-block-list\">\n<li>\u82e5\u662f\u7b2c\u00a0<code>size<\/code>\u00a0\u4e2a\uff08\u5373\u6700\u540e\u4e00\u4e2a\uff09\uff0c\u52a0\u5165\u7ed3\u679c\u5217\u8868\u3002<\/li>\n\n\n\n<li>\u5c06\u5176\u5de6\u53f3\u5b50\u8282\u70b9\uff08\u82e5\u5b58\u5728\uff09\u5165\u961f\uff0c\u4f9b\u4e0b\u4e00\u5c42\u4f7f\u7528\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>\u8fd4\u56de\u7ed3\u679c\u5217\u8868\u3002<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\">\u4e3a\u4ec0\u4e48\u5148\u52a0\u5de6\u5b50\u8282\u70b9\uff0c\u518d\u52a0\u53f3\u5b50\u8282\u70b9\uff1f<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u56e0\u4e3a\u6211\u4eec\u9700\u8981<strong>\u4ece\u5de6\u5230\u53f3\u904d\u5386\u5f53\u524d\u5c42<\/strong>\uff0c\u624d\u80fd\u786e\u4fdd\u6700\u540e\u4e00\u4e2a\u8282\u70b9\u662f<strong>\u6700\u53f3\u8fb9\u7684<\/strong>\u3002<\/li>\n\n\n\n<li>\u5982\u679c\u5148\u52a0\u53f3\u518d\u52a0\u5de6\uff0c\u867d\u7136\u4e5f\u80fd\u53d6\u5230\u6700\u540e\u4e00\u4e2a\uff0c\u4f46\u4e0d\u7b26\u5408\u5e38\u89c4\u5c42\u5e8f\u903b\u8f91\uff0c\u4e14\u53ef\u80fd\u5f71\u54cd\u5176\u4ed6\u53d8\u79cd\u9898\u3002<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>\ud83d\udd17 \u4e8c\u53c9\u6811\u7684\u53f3\u89c6\u56fe \u9898\u76ee\u6765\u6e90\uff1a199. \u4e8c\u53c9\u6811\u7684\u53f3\u89c6\u56fe &#8211; \u529b\u6263\uff08LeetCode\uff09 \ud83d\udccc \u9898\u76ee\u63cf\u8ff0 [&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":[57,59,14],"class_list":["post-438","post","type-post","status-publish","format-standard","hentry","category-binary_tree","category-algorithm","tag-binary_tree","tag-bfs","tag-algorithm"],"_links":{"self":[{"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/posts\/438","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=438"}],"version-history":[{"count":2,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/posts\/438\/revisions"}],"predecessor-version":[{"id":445,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/posts\/438\/revisions\/445"}],"wp:attachment":[{"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/media?parent=438"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/categories?post=438"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/tags?post=438"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}