{"id":382,"date":"2025-09-10T18:35:17","date_gmt":"2025-09-10T10:35:17","guid":{"rendered":"https:\/\/heyingnian.com\/?p=382"},"modified":"2025-09-10T18:35:39","modified_gmt":"2025-09-10T10:35:39","slug":"leetcode-19","status":"publish","type":"post","link":"https:\/\/heyingnian.com\/index.php\/2025\/09\/10\/leetcode-19\/","title":{"rendered":"\u5220\u9664\u94fe\u8868\u7684\u5012\u6570\u7b2c N \u4e2a\u7ed3\u70b9"},"content":{"rendered":"\n<h1 class=\"wp-block-heading\">\ud83d\udd17 \u5220\u9664\u94fe\u8868\u7684\u5012\u6570\u7b2c N \u4e2a\u7ed3\u70b9<\/h1>\n\n\n\n<p>\u9898\u76ee\u6765\u6e90\uff1a<a target=\"_blank\" rel=\"noreferrer noopener\"><a href=\"https:\/\/leetcode.cn\/problems\/remove-nth-node-from-end-of-list\/description\/?envType=study-plan-v2&amp;envId=top-100-liked\" target=\"_blank\" rel=\"noopener\">19. \u5220\u9664\u94fe\u8868\u7684\u5012\u6570\u7b2c N \u4e2a\u7ed3\u70b9 &#8211; \u529b\u6263\uff08LeetCode\uff09<\/a><\/a><\/p>\n\n\n\n<p>\ud83d\udccc \u9898\u76ee\u63cf\u8ff0<\/p>\n\n\n\n<p>\u7ed9\u4f60\u4e00\u4e2a\u94fe\u8868\uff0c\u5220\u9664\u94fe\u8868\u7684<strong>\u5012\u6570\u7b2c n \u4e2a\u7ed3\u70b9<\/strong>\uff0c\u5e76\u8fd4\u56de\u94fe\u8868\u7684<strong>\u5934\u7ed3\u70b9<\/strong>\u3002<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u94fe\u8868\u7ed3\u70b9\u6570\u00a0<code>sz<\/code>\u00a0\u6ee1\u8db3\u00a0<code>1 &lt;= sz &lt;= 30<\/code><\/li>\n\n\n\n<li><code>1 &lt;= n &lt;= sz<\/code>\uff08\u4fdd\u8bc1 n \u6709\u6548\uff0c\u4e0d\u4f1a\u8d8a\u754c\uff09<\/li>\n\n\n\n<li>\u7ed3\u70b9\u503c\u8303\u56f4\uff1a<code>0 &lt;= Node.val &lt;= 100<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u2705 \u793a\u4f8b\u89e3\u6790<\/p>\n\n\n\n<p>\u793a\u4f8b 1\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\/09\/image-23.png'><img class=\"lazyload lazyload-style-1\" src=\"data:image\/svg+xml;base64,PCEtLUFyZ29uTG9hZGluZy0tPgo8c3ZnIHdpZHRoPSIxIiBoZWlnaHQ9IjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgc3Ryb2tlPSIjZmZmZmZmMDAiPjxnPjwvZz4KPC9zdmc+\"  loading=\"lazy\" decoding=\"async\" width=\"542\" height=\"222\" data-original=\"https:\/\/heyingnian.com\/wp-content\/uploads\/2025\/09\/image-23.png\" src=\"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB\/AAffA0nNPuCLAAAAAElFTkSuQmCC\" alt=\"\" class=\"wp-image-383\"  sizes=\"auto, (max-width: 542px) 100vw, 542px\" \/><\/div><\/figure>\n\n\n\n<p>\u8f93\u5165\uff1a<code>head = [1,2,3,4,5]<\/code>, <code>n = 2<\/code><br>\u8f93\u51fa\uff1a<code>[1,2,3,5]<\/code><br>\u89e3\u91ca\uff1a\u5012\u6570\u7b2c 2 \u4e2a\u7ed3\u70b9\u662f\u503c\u4e3a 4 \u7684\u7ed3\u70b9\uff0c\u5220\u9664\u540e\u94fe\u8868\u53d8\u4e3a 1\u21922\u21923\u21925\u3002<\/p>\n\n\n\n<p>\u793a\u4f8b 2\uff1a<\/p>\n\n\n\n<p>\u8f93\u5165\uff1a<code>head = [1]<\/code>, <code>n = 1<\/code><br>\u8f93\u51fa\uff1a<code>[]<\/code><br>\u89e3\u91ca\uff1a\u94fe\u8868\u53ea\u6709\u4e00\u4e2a\u7ed3\u70b9\uff0c\u5220\u9664\u540e\u4e3a\u7a7a\u3002<\/p>\n\n\n\n<p>\u793a\u4f8b 3\uff1a<\/p>\n\n\n\n<p>\u8f93\u5165\uff1a<code>head = [1,2]<\/code>, <code>n = 1<\/code><br>\u8f93\u51fa\uff1a<code>[1]<\/code><br>\u89e3\u91ca\uff1a\u5220\u9664\u5012\u6570\u7b2c 1 \u4e2a\uff08\u5373\u6700\u540e\u4e00\u4e2a\uff09\u7ed3\u70b9 2\u3002<\/p>\n\n\n\n<p>\u26a0\ufe0f \u63d0\u793a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u94fe\u8868\u4e2d\u7ed3\u70b9\u7684\u6570\u76ee\u4e3a\u00a0<code>sz<\/code><\/li>\n\n\n\n<li><code>1 &lt;= sz &lt;= 30<\/code><\/li>\n\n\n\n<li><code>0 &lt;= Node.val &lt;= 100<\/code><\/li>\n\n\n\n<li><code>1 &lt;= n &lt;= sz<\/code><\/li>\n<\/ul>\n\n\n\n<p>\ud83d\udca1 \u89e3\u6cd5\uff1a\u5feb\u6162\u6307\u9488 + \u865a\u62df\u5934\u8282\u70b9 \u2014\u2014 O(n) \u65f6\u95f4\uff0cO(1) \u7a7a\u95f4<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>class Solution {\n    public ListNode removeNthFromEnd(ListNode head, int n) {\n        ListNode dummy = new ListNode(-1);\n        dummy.next = head;\n        ListNode fast = dummy;\n        ListNode slow = dummy;\n        \n        \/\/ \u7b2c\u4e00\u6b65\uff1afast \u5148\u8d70 n \u6b65\n        for (int i = 0; i &lt; n; i++) {\n            fast = fast.next;\n        }\n        \n        \/\/ \u7b2c\u4e8c\u6b65\uff1afast \u548c slow \u540c\u65f6\u524d\u8fdb\uff0c\u76f4\u5230 fast \u5230\u8fbe\u6700\u540e\u4e00\u4e2a\u8282\u70b9\n        while (fast.next != null) {\n            fast = fast.next;\n            slow = slow.next;\n        }\n        \n        \/\/ \u7b2c\u4e09\u6b65\uff1a\u5220\u9664 slow.next\uff08\u5373\u5012\u6570\u7b2c n \u4e2a\u8282\u70b9\uff09\n        slow.next = slow.next.next;\n        \n        \/\/ \u7b2c\u56db\u6b65\uff1a\u8fd4\u56de\u771f\u5b9e\u5934\u8282\u70b9\n        return dummy.next;\n    }\n}<\/code><\/pre>\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>\u5feb\u6307\u9488\u5148\u8d70 n \u6b65\uff0c\u518d\u4e0e\u6162\u6307\u9488\u540c\u6b65\u8d70\u5230\u5c3e\uff0c\u603b\u5171\u4e0d\u8d85\u8fc7 2n \u6b65 \u2192 \u7ebf\u6027\u65f6\u95f4\u3002<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>\u7a7a\u95f4\u590d\u6742\u5ea6\uff1aO(1) \u2705<\/strong>\n<ul class=\"wp-block-list\">\n<li>\u4ec5\u4f7f\u7528\u5e38\u6570\u4e2a\u6307\u9488\uff08<code>dummy<\/code>,\u00a0<code>fast<\/code>,\u00a0<code>slow<\/code>\uff09\uff0c\u65e0\u9012\u5f52\u3001\u65e0\u989d\u5916\u6570\u7ec4\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<p>\ud83e\udde9 \u89e3\u9898\u601d\u8def<\/p>\n\n\n\n<p>\u6838\u5fc3\u601d\u60f3\uff1a\u53cc\u6307\u9488\uff08\u5feb\u6162\u6307\u9488\uff09\u5b9a\u4f4d\u5012\u6570\u7b2c n \u4e2a\u8282\u70b9\u7684\u524d\u9a71\u8282\u70b9<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>\u4e3a\u4ec0\u4e48\u7528\u865a\u62df\u5934\u8282\u70b9\uff1f\n<ul class=\"wp-block-list\">\n<li>\u907f\u514d\u5220\u9664\u5934\u8282\u70b9\u65f6\u7684\u7279\u6b8a\u5904\u7406\uff08\u5982\u793a\u4f8b2\uff1a<code>[1], n=1<\/code>\uff09\u3002<\/li>\n\n\n\n<li>\u7edf\u4e00\u6240\u6709\u5220\u9664\u64cd\u4f5c\uff1a\u603b\u662f\u5220\u9664\u00a0<code>slow.next<\/code>\u3002<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>\u5feb\u6162\u6307\u9488\u539f\u7406\uff1a\n<ul class=\"wp-block-list\">\n<li><code>fast<\/code>\u00a0\u5148\u8d70\u00a0<code>n<\/code>\u00a0\u6b65 \u2192 \u6b64\u65f6\u00a0<code>fast<\/code>\u00a0\u4e0e\u00a0<code>slow<\/code>\u00a0\u76f8\u8ddd\u00a0<code>n<\/code>\u00a0\u4e2a\u8282\u70b9\u3002<\/li>\n\n\n\n<li>\u7136\u540e\u00a0<code>fast<\/code>\u00a0\u548c\u00a0<code>slow<\/code>\u00a0\u540c\u65f6\u524d\u8fdb\uff0c\u76f4\u5230\u00a0<code>fast.next == null<\/code>\uff08\u5373\u00a0<code>fast<\/code>\u00a0\u5230\u8fbe\u5c3e\u8282\u70b9\uff09\u3002<\/li>\n\n\n\n<li>\u6b64\u65f6\u00a0<code>slow<\/code>\u00a0\u6070\u597d\u505c\u5728<strong>\u5012\u6570\u7b2c n \u4e2a\u8282\u70b9\u7684\u524d\u4e00\u4e2a\u8282\u70b9<\/strong>\u3002<\/li>\n\n\n\n<li>\u6267\u884c\u00a0<code>slow.next = slow.next.next<\/code>\u00a0\u5373\u53ef\u5220\u9664\u76ee\u6807\u8282\u70b9\u3002<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>\u4e3e\u4f8b\u8bf4\u660e\uff1a<\/li>\n<\/ol>\n\n\n\n<p>\u8f93\u5165\uff1a<code>head = [1,2,3,4,5]<\/code>, <code>n = 2<\/code><\/p>\n\n\n\n<pre class=\"wp-block-preformatted\"><code>\u521d\u59cb\uff1a<br>dummy \u2192 1 \u2192 2 \u2192 3 \u2192 4 \u2192 5<br>slow^   fast^\uff08\u5148\u8d702\u6b65\u540e\uff09<br><br>\u7b2c1\u6b65\uff1afast \u8d702\u6b65 \u2192 \u505c\u5728 2<br>dummy \u2192 1 \u2192 2 \u2192 3 \u2192 4 \u2192 5<br>slow^       fast^<br><br>\u7b2c2\u6b65\uff1afast \u548c slow \u540c\u6b65\u524d\u8fdb\uff0c\u76f4\u5230 fast.next == null<br>dummy \u2192 1 \u2192 2 \u2192 3 \u2192 4 \u2192 5<br>            slow^     fast^<br><br>\u6b64\u65f6 slow.next \u662f 4\uff08\u5012\u6570\u7b2c2\u4e2a\uff09\uff0c\u6267\u884c slow.next = slow.next.next<br>\u2192 3 \u2192 5\uff0c\u8df3\u8fc7 4<br><br>\u7ed3\u679c\uff1adummy.next \u2192 1\u21922\u21923\u21925 \u2705<\/code><\/pre>\n\n\n\n<p>\u8fb9\u754c\u5904\u7406\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u5220\u9664\u5934\u8282\u70b9\uff08n = sz\uff09\u2192\u00a0<code>fast<\/code>\u00a0\u8d70 n \u6b65\u540e\uff0c<code>slow<\/code>\u00a0\u4ecd\u5728\u00a0<code>dummy<\/code>\uff0c<code>slow.next = head<\/code>\uff0c\u5220\u9664\u540e\u8fd4\u56de\u00a0<code>dummy.next<\/code>\u3002<\/li>\n\n\n\n<li>\u5220\u9664\u5c3e\u8282\u70b9\uff08n = 1\uff09\u2192\u00a0<code>fast<\/code>\u00a0\u8d701\u6b65\u540e\u4e0e\u00a0<code>slow<\/code>\u00a0\u540c\u6b65\u524d\u8fdb\uff0c\u6700\u7ec8\u00a0<code>slow<\/code>\u00a0\u505c\u5728\u5012\u6570\u7b2c\u4e8c\u4e2a\u8282\u70b9\uff0c\u5220\u9664\u6700\u540e\u4e00\u4e2a\u3002<\/li>\n\n\n\n<li>\u5355\u8282\u70b9\u94fe\u8868 \u2192\u00a0<code>fast<\/code>\u00a0\u8d701\u6b65\u5230\u552f\u4e00\u8282\u70b9\uff0c<code>while<\/code>\u00a0\u4e0d\u6267\u884c\uff0c<code>slow<\/code>\u00a0\u5728\u00a0<code>dummy<\/code>\uff0c\u5220\u9664\u00a0<code>slow.next<\/code>\u00a0\u2192 \u8fd4\u56de\u00a0<code>null<\/code>\u3002<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>\ud83d\udd17 \u5220\u9664\u94fe\u8868\u7684\u5012\u6570\u7b2c N \u4e2a\u7ed3\u70b9 \u9898\u76ee\u6765\u6e90\uff1a19. \u5220\u9664\u94fe\u8868\u7684\u5012\u6570\u7b2c N \u4e2a\u7ed3\u70b9 &#8211; \u529b\u6263\uff08Lee [&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-382","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\/382","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=382"}],"version-history":[{"count":1,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/posts\/382\/revisions"}],"predecessor-version":[{"id":384,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/posts\/382\/revisions\/384"}],"wp:attachment":[{"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/media?parent=382"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/categories?post=382"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/tags?post=382"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}