{"id":300,"date":"2025-08-29T10:41:43","date_gmt":"2025-08-29T02:41:43","guid":{"rendered":"https:\/\/heyingnian.com\/?p=300"},"modified":"2025-08-29T10:42:05","modified_gmt":"2025-08-29T02:42:05","slug":"leetcode-41","status":"publish","type":"post","link":"https:\/\/heyingnian.com\/index.php\/2025\/08\/29\/leetcode-41\/","title":{"rendered":"\u7f3a\u5931\u7684\u7b2c\u4e00\u4e2a\u6b63\u6570"},"content":{"rendered":"\n<h1 class=\"wp-block-heading\">\ud83d\udd17 \u7f3a\u5931\u7684\u7b2c\u4e00\u4e2a\u6b63\u6570<\/h1>\n\n\n\n<p>\u9898\u76ee\u6765\u6e90\uff1a<a target=\"_blank\" rel=\"noreferrer noopener\"><a href=\"https:\/\/leetcode.cn\/problems\/first-missing-positive\/?envType=study-plan-v2&amp;envId=top-100-liked\" target=\"_blank\" rel=\"noopener\">41. \u7f3a\u5931\u7684\u7b2c\u4e00\u4e2a\u6b63\u6570 &#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\u672a\u6392\u5e8f\u7684\u6574\u6570\u6570\u7ec4 <code>nums<\/code>\uff0c\u8bf7\u4f60\u627e\u51fa\u5176\u4e2d<strong>\u6ca1\u6709\u51fa\u73b0\u7684\u6700\u5c0f\u7684\u6b63\u6574\u6570<\/strong>\u3002<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u8981\u6c42<\/strong>\uff1a\n<ul class=\"wp-block-list\">\n<li>\u65f6\u95f4\u590d\u6742\u5ea6\u4e3a\u00a0<code>O(n)<\/code>\u3002<\/li>\n\n\n\n<li>\u53ea\u4f7f\u7528<strong>\u5e38\u6570\u7ea7\u522b\u989d\u5916\u7a7a\u95f4<\/strong>\uff08\u5373\u4e0d\u80fd\u4f7f\u7528\u54c8\u5e0c\u8868\u7b49\u989d\u5916\u6570\u636e\u7ed3\u6784\uff09\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>\u2705 \u793a\u4f8b\u89e3\u6790<\/p>\n\n\n\n<p>\u793a\u4f8b 1\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u8f93\u5165\uff1a<code>nums = [1,2,0]<\/code><\/li>\n\n\n\n<li>\u8f93\u51fa\uff1a<code>3<\/code><\/li>\n\n\n\n<li>\u89e3\u91ca\uff1a\u6b63\u6574\u6570\u00a0<code>1<\/code>\u00a0\u548c\u00a0<code>2<\/code>\u00a0\u90fd\u5728\u6570\u7ec4\u4e2d\uff0c\u6700\u5c0f\u7f3a\u5931\u7684\u662f\u00a0<code>3<\/code>\u3002<\/li>\n<\/ul>\n\n\n\n<p>\u793a\u4f8b 2\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u8f93\u5165\uff1a<code>nums = [3,4,-1,1]<\/code><\/li>\n\n\n\n<li>\u8f93\u51fa\uff1a<code>2<\/code><\/li>\n\n\n\n<li>\u89e3\u91ca\uff1a<code>1<\/code>\u00a0\u5b58\u5728\uff0c\u4f46\u00a0<code>2<\/code>\u00a0\u4e0d\u5b58\u5728\uff0c\u56e0\u6b64\u7b54\u6848\u662f\u00a0<code>2<\/code>\u3002<\/li>\n<\/ul>\n\n\n\n<p>\u793a\u4f8b 3\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u8f93\u5165\uff1a<code>nums = [7,8,9,11,12]<\/code><\/li>\n\n\n\n<li>\u8f93\u51fa\uff1a<code>1<\/code><\/li>\n\n\n\n<li>\u89e3\u91ca\uff1a\u6700\u5c0f\u7684\u6b63\u6574\u6570\u00a0<code>1<\/code>\u00a0\u6ca1\u6709\u51fa\u73b0\u5728\u6570\u7ec4\u4e2d\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><code>1 &lt;= nums.length &lt;= 10\u2075<\/code><\/li>\n\n\n\n<li><code>-2\u00b3\u00b9 &lt;= nums[i] &lt;= 2\u00b3\u00b9 - 1<\/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\u539f\u5730\u54c8\u5e0c\uff08\u5229\u7528\u6570\u7ec4\u7d22\u5f15\uff09\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 int firstMissingPositive(int&#91;] nums) {\n        int len = nums.length;\n\n        for (int i = 0; i &lt; len; i++) {\n            if (nums&#91;i] &lt;= 0) {\n                nums&#91;i] = len + 1;\n            }\n        }\n\n        for (int i = 0; i &lt; len; i++) {\n            int p = Math.abs(nums&#91;i]);\n            if (p &lt;= len) {\n                nums&#91;p - 1] = -Math.abs(nums&#91;p - 1]);\n            }\n        }\n        \n        for (int i = 0; i &lt; len; i++) {\n            if (nums&#91;i] > 0) {\n                return i + 1;\n            }\n        }\n \n        return len + 1;\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>\u4e09\u6b21\u904d\u5386\u6570\u7ec4\uff0c\u6bcf\u6b21 O(n)\uff0c\u603b\u4f53\u4e3a\u7ebf\u6027\u65f6\u95f4\u3002<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>\u7a7a\u95f4\u590d\u6742\u5ea6\uff1aO(1)<\/strong>\n<ul class=\"wp-block-list\">\n<li>\u4ec5\u4f7f\u7528\u5e38\u6570\u4e2a\u989d\u5916\u53d8\u91cf\uff08\u5982\u00a0<code>i<\/code>,\u00a0<code>p<\/code>\uff09<\/li>\n\n\n\n<li>\u6240\u6709\u64cd\u4f5c\u5747\u5728\u539f\u6570\u7ec4\u00a0<code>nums<\/code>\u00a0\u4e0a\u8fdb\u884c\uff0c\u672a\u4f7f\u7528\u989d\u5916\u6570\u7ec4\u6216\u54c8\u5e0c\u8868\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\u539f\u5730\u54c8\u5e0c\uff08Index as Hash Key\uff09<\/strong>\n<ul class=\"wp-block-list\">\n<li>\u6570\u7ec4\u957f\u5ea6\u4e3a\u00a0<code>n<\/code>\uff0c\u5219\u6700\u5c0f\u7f3a\u5931\u6b63\u6570\u4e00\u5b9a\u5728\u00a0<code>[1, n+1]<\/code>\u00a0\u8303\u56f4\u5185\u3002<\/li>\n\n\n\n<li>\u5229\u7528\u6570\u7ec4<strong>\u7d22\u5f15\u00a0<code>i<\/code><\/strong>\u00a0\u6765\u8868\u793a\u6570\u5b57\u00a0<code>i+1<\/code>\u00a0\u662f\u5426\u5b58\u5728\u3002<\/li>\n\n\n\n<li>\u901a\u8fc7<strong>\u8d1f\u53f7<\/strong>\u6807\u8bb0\u67d0\u4e2a\u4f4d\u7f6e\u662f\u5426\u88ab\u201c\u5360\u7528\u201d\u3002<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>\u4e09\u6b65\u8d70\u7b56\u7565<\/strong>\uff1a\u00a0<strong>\u6b65\u9aa4 1\uff1a\u9884\u5904\u7406\uff0c\u6e05\u9664\u5e72\u6270\u9879<\/strong><ul><li>\u5c06\u6240\u6709\u00a0<code>&lt;= 0<\/code>\u00a0\u7684\u6570\u66ff\u6362\u4e3a\u00a0<code>n + 1<\/code>\uff08\u4e00\u4e2a\u8d85\u51fa\u8303\u56f4\u7684\u6570\uff09<\/li><li>\u76ee\u7684\uff1a\u786e\u4fdd\u6570\u7ec4\u4e2d\u6240\u6709\u6570\u90fd\u662f\u6b63\u6570\uff0c\u4fbf\u4e8e\u540e\u7eed\u7528\u8d1f\u53f7\u6807\u8bb0\u3002<\/li><\/ul><strong>\u6b65\u9aa4 2\uff1a\u6807\u8bb0\u5b58\u5728\u7684\u6570<\/strong><ul><li>\u904d\u5386\u6bcf\u4e2a\u5143\u7d20\u00a0<code>nums[i]<\/code>\uff0c\u53d6\u5176\u7edd\u5bf9\u503c\u00a0<code>p = |nums[i]|<\/code><\/li><li>\u82e5\u00a0<code>p &lt;= n<\/code>\uff0c\u8bf4\u660e\u00a0<code>p<\/code>\u00a0\u662f\u4e00\u4e2a\u6709\u6548\u7684\u6b63\u6570\uff08\u5728\u00a0<code>1~n<\/code>\u00a0\u8303\u56f4\u5185\uff09<\/li><li>\u5c06\u00a0<code>nums[p - 1]<\/code>\u00a0\u8bbe\u4e3a\u8d1f\u6570\uff08<code>-|nums[p-1]|<\/code>\uff09\uff0c\u8868\u793a\u6570\u5b57\u00a0<code>p<\/code>\u00a0\u5b58\u5728<\/li><li>\u4f7f\u7528\u00a0<code>Math.abs<\/code>\u00a0\u662f\u4e3a\u4e86\u907f\u514d\u91cd\u590d\u8bbf\u95ee\u65f6\u56e0\u8d1f\u6570\u5bfc\u81f4\u9519\u8bef\u3002<\/li><\/ul><strong>\u6b65\u9aa4 3\uff1a\u67e5\u627e\u7b2c\u4e00\u4e2a\u672a\u6807\u8bb0\u7684\u4f4d\u7f6e<\/strong>\n<ul class=\"wp-block-list\">\n<li>\u518d\u6b21\u904d\u5386\u6570\u7ec4\uff0c\u627e\u5230\u7b2c\u4e00\u4e2a\u00a0<code>nums[i] > 0<\/code>\u00a0\u7684\u4f4d\u7f6e<\/li>\n\n\n\n<li>\u8bf4\u660e\u6570\u5b57\u00a0<code>i + 1<\/code>\u00a0\u4e0d\u5b58\u5728\uff0c\u8fd4\u56de\u00a0<code>i + 1<\/code><\/li>\n\n\n\n<li>\u82e5\u6240\u6709\u4f4d\u7f6e\u90fd\u00a0<code>&lt;= 0<\/code>\uff0c\u8bf4\u660e\u00a0<code>1~n<\/code>\u00a0\u90fd\u5b58\u5728\uff0c\u8fd4\u56de\u00a0<code>n + 1<\/code><\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>\u4e3e\u4f8b\u8bf4\u660e<\/strong>\uff1a<br>\u5bf9 <code>nums = [3,4,-1,1]<\/code>\uff1a\n<ul class=\"wp-block-list\">\n<li>Step 1 \u540e\uff1a<code>[3,4,5,1]<\/code>\uff08<code>-1<\/code>\u00a0\u2192\u00a0<code>5<\/code>\uff09<\/li>\n\n\n\n<li>Step 2 \u8fc7\u7a0b\uff1a\n<ul class=\"wp-block-list\">\n<li>i=0: p=3 \u2264 4 \u2192 nums[2] = -5 \u2192\u00a0<code>[3,4,-5,1]<\/code><\/li>\n\n\n\n<li>i=1: p=4 \u2264 4 \u2192 nums[3] = -1 \u2192\u00a0<code>[3,4,-5,-1]<\/code><\/li>\n\n\n\n<li>i=2: p=5 > 4 \u2192 \u5ffd\u7565<\/li>\n\n\n\n<li>i=3: p=1 \u2264 4 \u2192 nums[0] = -3 \u2192\u00a0<code>[-3,4,-5,-1]<\/code><\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>Step 3\uff1a<code>nums[1] = 4 > 0<\/code>\u00a0\u2192 \u8fd4\u56de\u00a0<code>1 + 1 = 2<\/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>\u6240\u6709\u6570\u90fd\u4e3a\u6b63\u4e14\u8fde\u7eed\uff08\u5982\u00a0<code>[1,2,3]<\/code>\uff09\u2192 \u8fd4\u56de\u00a0<code>4<\/code><\/li>\n\n\n\n<li>\u6240\u6709\u6570\u90fd\u5927\u4e8e\u00a0<code>n<\/code>\uff08\u5982\u00a0<code>[7,8,9]<\/code>\uff09\u2192 \u8fd4\u56de\u00a0<code>1<\/code><\/li>\n<\/ul>\n<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"<p>\ud83d\udd17 \u7f3a\u5931\u7684\u7b2c\u4e00\u4e2a\u6b63\u6570 \u9898\u76ee\u6765\u6e90\uff1a41. \u7f3a\u5931\u7684\u7b2c\u4e00\u4e2a\u6b63\u6570 &#8211; \u529b\u6263\uff08LeetCode\uff09 \ud83d\udccc \u9898\u76ee\u63cf [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[30,12],"tags":[15,14],"class_list":["post-300","post","type-post","status-publish","format-standard","hentry","category-ordinary_arrays","category-algorithm","tag-hash","tag-algorithm"],"_links":{"self":[{"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/posts\/300","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=300"}],"version-history":[{"count":1,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/posts\/300\/revisions"}],"predecessor-version":[{"id":301,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/posts\/300\/revisions\/301"}],"wp:attachment":[{"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/media?parent=300"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/categories?post=300"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/heyingnian.com\/index.php\/wp-json\/wp\/v2\/tags?post=300"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}