{"id":361,"date":"2025-09-05T10:48:52","date_gmt":"2025-09-05T02:48:52","guid":{"rendered":"https:\/\/heyingnian.com\/?p=361"},"modified":"2025-09-05T10:56:48","modified_gmt":"2025-09-05T02:56:48","slug":"leetcode-234","status":"publish","type":"post","link":"https:\/\/heyingnian.com\/index.php\/2025\/09\/05\/leetcode-234\/","title":{"rendered":"\u56de\u6587\u94fe\u8868"},"content":{"rendered":"\n<h1 class=\"wp-block-heading\">\ud83d\udd17 \u56de\u6587\u94fe\u8868<\/h1>\n\n\n\n<p>\u9898\u76ee\u6765\u6e90\uff1a<a target=\"_blank\" rel=\"noreferrer noopener\"><a href=\"https:\/\/leetcode.cn\/problems\/palindrome-linked-list\/submissions\/659707435\/?envType=study-plan-v2&amp;envId=top-100-liked\" target=\"_blank\" rel=\"noopener\">234. \u56de\u6587\u94fe\u8868 &#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<p>\ud83d\udccc \u9898\u76ee\u63cf\u8ff0<\/p>\n\n\n\n<p>\u7ed9\u4f60\u4e00\u4e2a\u5355\u94fe\u8868\u7684\u5934\u8282\u70b9 <code>head<\/code>\uff0c\u8bf7\u4f60\u5224\u65ad\u8be5\u94fe\u8868\u662f\u5426\u4e3a<strong>\u56de\u6587\u94fe\u8868<\/strong>\u3002\u5982\u679c\u662f\uff0c\u8fd4\u56de <code>true<\/code>\uff1b\u5426\u5219\uff0c\u8fd4\u56de <code>false<\/code>\u3002<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u56de\u6587\u94fe\u8868<\/strong>\uff1a\u94fe\u8868\u4ece\u524d\u5f80\u540e\u8bfb\u548c\u4ece\u540e\u5f80\u524d\u8bfb\u662f\u4e00\u6837\u7684\u3002<br>\u4f8b\u5982\uff1a<code>1 \u2192 2 \u2192 2 \u2192 1<\/code>\u00a0\u662f\u56de\u6587\uff0c<code>1 \u2192 2<\/code>\u00a0\u4e0d\u662f\u3002<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p>\u2705 \u793a\u4f8b\u89e3\u6790<\/p>\n\n\n\n<p><strong>\u793a\u4f8b 1<\/strong>\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u8f93\u5165\uff1a<code>head = [1,2,2,1]<\/code><\/li>\n\n\n\n<li>\u8f93\u51fa\uff1a<code>true<\/code><\/li>\n\n\n\n<li>\u89e3\u91ca\uff1a\u6b63\u8bfb\u53cd\u8bfb\u90fd\u662f\u00a0<code>1,2,2,1<\/code>\u3002<\/li>\n<\/ul>\n\n\n\n<p><strong>\u793a\u4f8b 2<\/strong>\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u8f93\u5165\uff1a<code>head = [1,2]<\/code><\/li>\n\n\n\n<li>\u8f93\u51fa\uff1a<code>false<\/code><\/li>\n\n\n\n<li>\u89e3\u91ca\uff1a\u6b63\u8bfb\u662f\u00a0<code>1,2<\/code>\uff0c\u53cd\u8bfb\u662f\u00a0<code>2,1<\/code>\uff0c\u4e0d\u4e00\u81f4\u3002<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p>\u26a0\ufe0f \u63d0\u793a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u94fe\u8868\u4e2d\u8282\u70b9\u6570\u76ee\u5728\u8303\u56f4\u00a0<code>[1, 10\u2075]<\/code>\u00a0\u5185<\/li>\n\n\n\n<li><code>0 &lt;= Node.val &lt;= 9<\/code><\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p>\ud83d\udca1 \u89e3\u6cd5\uff1a\u5feb\u6162\u6307\u9488 + \u53cd\u8f6c\u540e\u534a\u90e8\u5206 \u2014\u2014 O(n) \u65f6\u95f4\uff0cO(1) \u7a7a\u95f4<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>class Solution {\n    \/\/ \u8f85\u52a9\u65b9\u6cd5\uff1a\u53cd\u8f6c\u94fe\u8868\n    public ListNode reverseList(ListNode head) {\n        ListNode res = null;\n        while (head != null) {\n            ListNode next = head.next;\n            head.next = res;\n            res = head;\n            head = next;\n        }\n        return res;\n    }\n\n    \/\/ \u4e3b\u65b9\u6cd5\uff1a\u5224\u65ad\u662f\u5426\u4e3a\u56de\u6587\u94fe\u8868\n    public boolean isPalindrome(ListNode head) {\n        if (head == null || head.next == null) {\n            return true; \/\/ \u7a7a\u94fe\u8868\u6216\u5355\u8282\u70b9\u89c6\u4e3a\u56de\u6587\n        }\n\n        \/\/ 1. \u4f7f\u7528\u5feb\u6162\u6307\u9488\u627e\u5230\u540e\u534a\u90e8\u5206\u7684\u8d77\u59cb\u8282\u70b9\n        ListNode fast = head, slow = head;\n        while (fast != null &amp;&amp; fast.next != null) {\n            fast = fast.next.next;\n            slow = slow.next;\n        }\n\n        \/\/ 2. \u5982\u679c\u94fe\u8868\u957f\u5ea6\u4e3a\u5947\u6570\uff0cslow \u9700\u8981\u518d\u524d\u8fdb\u4e00\u6b65\uff08\u8df3\u8fc7\u4e2d\u95f4\u8282\u70b9\uff09\n        if (fast != null) {\n            slow = slow.next;\n        }\n\n        \/\/ 3. \u53cd\u8f6c\u540e\u534a\u90e8\u5206\u94fe\u8868\n        ListNode reversed = reverseList(slow);\n\n        \/\/ 4. \u6bd4\u8f83\u524d\u534a\u90e8\u5206\u4e0e\u53cd\u8f6c\u540e\u7684\u540e\u534a\u90e8\u5206\n        while (reversed != null) {\n            if (reversed.val != head.val) {\n                return false;\n            }\n            reversed = reversed.next;\n            head = head.next;\n        }\n\n        return true;\n    }\n}<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p>\ud83d\udcca \u590d\u6742\u5ea6\u5206\u6790<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u65f6\u95f4\u590d\u6742\u5ea6\uff1aO(n)<\/strong>\n<ul class=\"wp-block-list\">\n<li>\u627e\u4e2d\u70b9\uff1aO(n\/2)<\/li>\n\n\n\n<li>\u53cd\u8f6c\u540e\u534a\u90e8\u5206\uff1aO(n\/2)<\/li>\n\n\n\n<li>\u6bd4\u8f83\u4e24\u90e8\u5206\uff1aO(n\/2)<\/li>\n\n\n\n<li>\u603b\u4f53\u4e3a O(n)<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>\u7a7a\u95f4\u590d\u6742\u5ea6\uff1aO(1)<\/strong> \u2705\n<ul class=\"wp-block-list\">\n<li>\u4ec5\u4f7f\u7528\u5e38\u6570\u4e2a\u989d\u5916\u6307\u9488\uff0c\u65e0\u9012\u5f52\u6216\u989d\u5916\u6570\u7ec4\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p>\ud83e\udde9 \u89e3\u9898\u601d\u8def<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u6838\u5fc3\u601d\u60f3\uff1a\u6bd4\u8f83\u524d\u534a\u90e8\u5206\u4e0e\u53cd\u8f6c\u540e\u7684\u540e\u534a\u90e8\u5206<\/strong>\n<ul class=\"wp-block-list\">\n<li>\u56de\u6587\u94fe\u8868\u7684\u7279\u6027\u662f\uff1a<strong>\u524d\u534a\u90e8\u5206 == \u53cd\u8f6c\u540e\u7684\u540e\u534a\u90e8\u5206<\/strong>\u3002<\/li>\n\n\n\n<li>\u56e0\u6b64\uff0c\u53ef\u4ee5\uff1a\n<ol class=\"wp-block-list\">\n<li>\u627e\u5230\u94fe\u8868\u4e2d\u70b9\uff1b<\/li>\n\n\n\n<li>\u53cd\u8f6c\u540e\u534a\u90e8\u5206\uff1b<\/li>\n\n\n\n<li>\u7528\u4e24\u4e2a\u6307\u9488\u5206\u522b\u4ece\u5934\u548c\u53cd\u8f6c\u540e\u7684\u540e\u534a\u90e8\u5206\u5f00\u59cb\u6bd4\u8f83\u3002<\/li>\n<\/ol>\n<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>\u6b65\u9aa4\u8be6\u89e3<\/strong>\uff1a\u00a0<strong>\u6b65\u9aa4 1\uff1a\u5feb\u6162\u6307\u9488\u627e\u4e2d\u70b9<\/strong><ul><li><code>fast<\/code>\u00a0\u6bcf\u6b21\u8d70\u4e24\u6b65\uff0c<code>slow<\/code>\u00a0\u6bcf\u6b21\u8d70\u4e00\u6b65\u3002<\/li><li>\u5f53\u00a0<code>fast<\/code>\u00a0\u5230\u8fbe\u672b\u5c3e\u65f6\uff0c<code>slow<\/code>\u00a0\u6b63\u597d\u5728\u4e2d\u70b9\u3002<\/li><li>\u9002\u7528\u4e8e\u5076\u6570\u548c\u5947\u6570\u957f\u5ea6\u94fe\u8868\u3002<\/li><\/ul><strong>\u6b65\u9aa4 2\uff1a\u5904\u7406\u5947\u6570\u957f\u5ea6\u94fe\u8868<\/strong><ul><li>\u5982\u679c\u00a0<code>fast != null<\/code>\uff0c\u8bf4\u660e\u94fe\u8868\u957f\u5ea6\u4e3a\u5947\u6570\uff08\u56e0\u4e3a\u00a0<code>fast<\/code>\u00a0\u8d70\u5230\u4e86\u6700\u540e\u4e00\u4e2a\u8282\u70b9\uff0c\u672a\u8d8a\u754c\uff09\u3002<\/li><li>\u6b64\u65f6\u00a0<code>slow<\/code>\u00a0\u6307\u5411\u4e2d\u95f4\u8282\u70b9\uff0c\u5e94\u8df3\u8fc7\u5b83\uff08<code>slow = slow.next<\/code>\uff09\uff0c\u56e0\u4e3a\u4e2d\u95f4\u8282\u70b9\u4e0d\u5f71\u54cd\u56de\u6587\u5224\u65ad\u3002<\/li><\/ul><strong>\u6b65\u9aa4 3\uff1a\u53cd\u8f6c\u540e\u534a\u90e8\u5206<\/strong><ul><li>\u8c03\u7528\u00a0<code>reverseList(slow)<\/code>\u00a0\u5f97\u5230\u53cd\u8f6c\u540e\u7684\u540e\u534a\u90e8\u5206\u94fe\u8868\u3002<\/li><\/ul><strong>\u6b65\u9aa4 4\uff1a\u9010\u4e00\u5bf9\u6bd4<\/strong>\n<ul class=\"wp-block-list\">\n<li>\u7528\u00a0<code>head<\/code>\u00a0\u4ece\u539f\u94fe\u8868\u5934\u5f00\u59cb\uff0c<code>reversed<\/code>\u00a0\u4ece\u53cd\u8f6c\u540e\u7684\u540e\u534a\u90e8\u5206\u5934\u5f00\u59cb\u3002<\/li>\n\n\n\n<li>\u9010\u4e2a\u6bd4\u8f83\u00a0<code>val<\/code>\uff0c\u4e00\u65e6\u4e0d\u540c\u7acb\u5373\u8fd4\u56de\u00a0<code>false<\/code>\u3002<\/li>\n\n\n\n<li>\u5982\u679c\u5168\u90e8\u76f8\u540c\uff0c\u8fd4\u56de\u00a0<code>true<\/code>\u3002<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>\u4e3e\u4f8b\u8bf4\u660e<\/strong>\uff1a\u00a0<strong>\u60c5\u51b5 1\uff1a\u5076\u6570\u957f\u5ea6<\/strong><code>1\u21922\u21922\u21921<\/code><ul><li>\u627e\u4e2d\u70b9\uff1a<code>slow<\/code>\u00a0\u505c\u5728\u7b2c\u4e8c\u4e2a\u00a0<code>2<\/code>\uff08\u7d22\u5f15 2\uff09<\/li><li><code>fast == null<\/code>\u00a0\u2192 \u4e0d\u8df3\u8fc7<\/li><li>\u540e\u534a\u90e8\u5206\uff1a<code>2\u21921<\/code>\uff0c\u53cd\u8f6c\u540e\u53d8\u4e3a\u00a0<code>1\u21922<\/code><\/li><li>\u6bd4\u8f83\u524d\u534a\u90e8\u5206\u00a0<code>1\u21922<\/code>\u00a0\u4e0e\u00a0<code>1\u21922<\/code>\u00a0\u2192 \u76f8\u7b49 \u2192\u00a0<code>true<\/code>\u00a0\u2705<\/li><\/ul><strong>\u60c5\u51b5 2\uff1a\u5947\u6570\u957f\u5ea6<\/strong><code>1\u21922\u21923\u21922\u21921<\/code>\n<ul class=\"wp-block-list\">\n<li><code>slow<\/code>\u00a0\u505c\u5728\u00a0<code>3<\/code><\/li>\n\n\n\n<li><code>fast != null<\/code>\u00a0\u2192\u00a0<code>slow = slow.next<\/code>\u00a0\u2192 \u6307\u5411\u7b2c\u4e00\u4e2a\u00a0<code>2<\/code><\/li>\n\n\n\n<li>\u540e\u534a\u90e8\u5206\uff1a<code>2\u21921<\/code>\uff0c\u53cd\u8f6c\u540e\u53d8\u4e3a\u00a0<code>1\u21922<\/code><\/li>\n\n\n\n<li>\u6bd4\u8f83\u524d\u534a\u90e8\u5206\u00a0<code>1\u21922<\/code>\u00a0\u4e0e\u00a0<code>1\u21922<\/code>\u00a0\u2192 \u76f8\u7b49 \u2192\u00a0<code>true<\/code>\u00a0\u2705<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>\u8fb9\u754c\u5904\u7406<\/strong>\uff1a\n<ul class=\"wp-block-list\">\n<li>\u7a7a\u94fe\u8868\uff1a<code>head == null<\/code>\u00a0\u2192 \u8fd4\u56de\u00a0<code>true<\/code>\u3002<\/li>\n\n\n\n<li>\u5355\u8282\u70b9\uff1a<code>head.next == null<\/code>\u00a0\u2192 \u8fd4\u56de\u00a0<code>true<\/code>\u3002<\/li>\n\n\n\n<li>\u4e24\u4e2a\u8282\u70b9\uff1a<code>slow<\/code>\u00a0\u505c\u5728\u7b2c\u4e8c\u4e2a\u8282\u70b9\uff0c<code>fast == null<\/code>\u00a0\u2192 \u4e0d\u8df3\u8fc7 \u2192 \u53cd\u8f6c\u7b2c\u4e8c\u4e2a\u8282\u70b9 \u2192 \u6bd4\u8f83\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"<p>\ud83d\udd17 \u56de\u6587\u94fe\u8868 \u9898\u76ee\u6765\u6e90\uff1a234. \u56de\u6587\u94fe\u8868 &#8211; \u529b\u6263\uff08LeetCode\uff09 \ud83d\udccc \u9898\u76ee\u63cf\u8ff0 \u7ed9\u4f60\u4e00\u4e2a\u5355 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[12,38],"tags":[16,14,51],"class_list":["post-361","post","type-post","status-publish","format-standard","hentry","category-algorithm","category-linked_list","tag-double_pointers","tag-algorithm","tag-linked_list"],"_links":{"self":[{"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/posts\/361","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=361"}],"version-history":[{"count":1,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/posts\/361\/revisions"}],"predecessor-version":[{"id":362,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/posts\/361\/revisions\/362"}],"wp:attachment":[{"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/media?parent=361"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/categories?post=361"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/tags?post=361"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}