{"id":300105,"date":"2022-11-24T14:27:12","date_gmt":"2022-11-24T13:27:12","guid":{"rendered":"https:\/\/blog.jetbrains.com\/?post_type=kotlin&#038;p=300105"},"modified":"2022-11-24T14:27:15","modified_gmt":"2022-11-24T13:27:15","slug":"kotlin-advent-of-code","status":"publish","type":"kotlin","link":"https:\/\/blog.jetbrains.com\/zh-hans\/kotlin\/2022\/11\/kotlin-advent-of-code\/","title":{"rendered":"\u4f7f\u7528\u60ef\u7528 Kotlin \u89e3\u51b3 Advent of Code \u8c1c\u9898"},"content":{"rendered":"<p>\u9664\u4e86\u7f16\u5199\u4ee3\u7801\u4e4b\u5916\uff0c\u5b66\u4e60\u4e00\u95e8\u8bed\u8a00\u6700\u597d\u7684\u65b9\u5f0f\u662f\u4ec0\u4e48\uff1f \u89e3\u51b3\u50cf <a href=\"https:\/\/adventofcode.com\/\" target=\"_blank\" rel=\"noopener\">Advent of Code<\/a> \u4e2d\u7684\u90a3\u4e9b\u6709\u8da3\u800c\u7b80\u77ed\u7684\u4efb\u52a1\u53ef\u80fd\u662f\u7ec3\u4e60\u8bed\u8a00\u6280\u80fd\u7684\u7edd\u4f73\u673a\u4f1a\uff0c\u5982\u679c\u5c06\u81ea\u5df1\u7684\u89e3\u51b3\u65b9\u6848\u4e0e\u5176\u4ed6\u4eba\u89e3\u51b3\u76f8\u540c\u95ee\u9898\u7684\u65b9\u5f0f\u8fdb\u884c\u6bd4\u8f83\uff0c\u60a8\u53ef\u4ee5\u5b66\u5230\u5f88\u591a\u4e1c\u897f\u3002<\/p>\n<p>\u6765\u81ea\u4e16\u754c\u5404\u5730\u7684\u8bb8\u591a\u5f00\u53d1\u8005\uff0c\u5305\u62ec\u6765\u81ea Kotlin \u56e2\u961f\u7684\u4e00\u4e9b\u5f00\u53d1\u8005\uff0c\u90fd\u4f1a\u53c2\u52a0 <a href=\"https:\/\/twitter.com\/ericwastl\" target=\"_blank\" rel=\"noopener\">Eric Wastl<\/a> \u521b\u5efa\u7684 Advent of Code \u6311\u6218\u3002 Advent of Code \u662f\u6bcf\u5e74 12 \u6708\u53d1\u5e03\u7684\u4e00\u7cfb\u5217\u4efb\u52a1\uff0c\u60a8\u53ef\u4ee5\u89e3\u51b3\u8fd9\u4e9b\u4efb\u52a1\u5e76\u4e0e\u4ed6\u4eba\u7ade\u4e89\u3002 \u8bb8\u591a\u4eba\u90fd\u8ba4\u540c\u8fd9\u662f\u5e86\u795d\u5723\u8bde\u8282\u548c\u65b0\u5e74\u7684\u6700\u597d\u7684\u5012\u8ba1\u65f6\u65e5\u5386\uff01<\/p>\n<p>\u4e3a\u4e86\u5e2e\u52a9\u793e\u533a\u5b66\u4e60\u60ef\u7528 Kotlin\uff0c\u5e76\u6fc0\u52b1\u66f4\u591a\u5f00\u53d1\u8005\u5c06\u6765\u7528 Kotlin \u89e3\u51b3 Advent of Code \u4efb\u52a1\uff0c\u6211\u4eec\u51b3\u5b9a\u4e3a Advent of Code 2020 \u7684\u4efb\u52a1\u51c6\u5907\u89e3\u51b3\u65b9\u6848\u3002 \u4e0d\u7ba1\u60a8\u5df2\u7ecf\u5728 12 \u6708\u89e3\u51b3\u4e86\u8fd9\u4e9b\u4efb\u52a1\uff0c\u51c6\u5907\u73b0\u5728\u89e3\u51b3\uff0c\u8fd8\u662f\u53ea\u60f3\u67e5\u770b\u89e3\u51b3\u65b9\u6848\uff0c\u6211\u4eec\u90fd\u5e0c\u671b\u60a8\u80fd\u5728\u8fd9\u4e9b\u6750\u6599\u4e2d\u6709\u6240\u6536\u83b7\u3002 \u5f53\u7136\uff0c\u5982\u679c\u60a8\u5148\u5c1d\u8bd5\u81ea\u5df1\u89e3\u51b3\u4efb\u52a1\uff0c\u6548\u679c\u4f1a\u66f4\u597d\uff01<\/p>\n<p>\u00a0<\/p>\n<p>\u4ee5\u4e0b\u662f\u7b2c\u4e00\u4e2a\u4efb\u52a1\u7684\u89e3\u51b3\u65b9\u6848\u548c\u89c6\u9891\u3002 \u5982\u679c\u60a8\u89c9\u5f97\u8fd9\u79cd\u5f62\u5f0f\u5f88\u6709\u7528\uff0c\u5e76\u5e0c\u671b\u6211\u4eec\u7528\u7c7b\u4f3c\u7684\u65b9\u5f0f\u6db5\u76d6\u66f4\u591a\u4efb\u52a1\uff0c\u8bf7\u5728\u8bc4\u8bba\u4e2d\u5206\u4eab\u60a8\u7684\u60f3\u6cd5\uff01<\/p>\n<h2>\u7b2c 1 \u5929. Report Repair<\/h2>\n<p>\u6211\u4eec\u8981\u4fee\u6b63\u4e00\u4efd\u8d39\u7528\u62a5\u544a\uff01 \u8bf7\u5728 <a href=\"https:\/\/adventofcode.com\/2020\/day\/1\" target=\"_blank\" rel=\"noopener\">https:\/\/adventofcode.com\/2020\/day\/1<\/a> \u67e5\u770b\u5b8c\u6574\u7684\u4efb\u52a1\u63cf\u8ff0*\u3002<\/p>\n<p>\u60a8\u9700\u8981\u4ece\u6570\u5b57\u5217\u8868\u4e2d\u627e\u5230\u548c\u4e3a 2020 \u7684\u4e24\u4e2a\uff08\u5728\u7b2c\u4e8c\u90e8\u5206\u4e2d\u662f\u4e09\u4e2a\uff09\u6761\u76ee\uff0c\u7136\u540e\u5c06\u8fd9\u4e24\u4e2a\uff08\u6216\u4e09\u4e2a\uff09\u6570\u5b57\u76f8\u4e58\u3002<\/p>\n<h3 id=\"how-to-solve\">\u5982\u4f55\u89e3\u51b3\u4efb\u52a1<\/h3>\n<p>\u5728 <a href=\"https:\/\/adventofcode.com\/\" target=\"_blank\" rel=\"noopener\">https:\/\/adventofcode.com\/<\/a> \u6ce8\u518c\uff0c\u6253\u5f00 <a href=\"https:\/\/adventofcode.com\/2020\/day\/1\" target=\"_blank\" rel=\"noopener\">https:\/\/adventofcode.com\/2020\/day\/1<\/a> \u4e0b\u7684\u4efb\u52a1\uff0c\u4f7f\u7528 Kotlin \u7f16\u5199\u60a8\u7684\u89e3\u51b3\u65b9\u6848\uff0c\u7136\u540e\u5728\u7f51\u7ad9\u4e0a\u68c0\u67e5\u7ed3\u679c\u3002 \u60a8\u53ef\u4ee5<a href=\"https:\/\/play.kotlinlang.org\/\" target=\"_blank\" rel=\"noopener\">\u5728\u7ebf<\/a>\u7f16\u5199 Kotlin \u4ee3\u7801\uff0c\u4e5f\u53ef\u4ee5\u4f7f\u7528 IDE\uff1a<\/p>\n<ul>\n<li>\u4e0b\u8f7d\u514d\u8d39\u7684\u793e\u533a\u7248 <a href=\"https:\/\/www.jetbrains.com\/idea\/download\/\" target=\"_blank\" rel=\"noopener\">IntelliJ IDEA<\/a><\/li>\n<li>\u521b\u5efa<a href=\"https:\/\/kotlinlang.org\/docs\/jvm-get-started.html\" target=\"_blank\" rel=\"noopener\">\u4e00\u4e2a Kotlin \u9879\u76ee<\/a><\/li>\n<li>\u5728\u9879\u76ee\u4e2d\u7f16\u5199\u89e3\u51b3\u65b9\u6848<\/li>\n<\/ul>\n<p>\u6700\u540e\uff0c\u5c06\u60a8\u7684\u89e3\u51b3\u65b9\u6848\u4e0e\u4e0b\u9762\u7684\u89e3\u51b3\u65b9\u6848\u8fdb\u884c\u6bd4\u8f83\u3002<\/p>\n<p>\u6211\u4eec\u5c06 <code>src<\/code> \u6587\u4ef6\u5939<a href=\"https:\/\/github.com\/svtk\/advent-of-code-2020\/blob\/master\/build.gradle.kts\" target=\"_blank\" rel=\"noopener\">\u6807\u8bb0<\/a>\u4e3a\u6e90\u96c6\uff0c\u5c06\u4ee3\u7801\u76f4\u63a5\u653e\u5728\u90a3\u91cc\u3002 \u4e3a\u65b9\u4fbf\u8d77\u89c1\uff0c\u6211\u4eec\u5c06\u8f93\u5165\u6587\u4ef6\uff08\u5982 <code>src\/day1\/input.txt<\/code>\uff09\u590d\u5236\u5230\u6e90\u6587\u4ef6\u5939\u3002 \u60a8\u53ef\u4ee5\u5728<a href=\"https:\/\/github.com\/Kotlin-hands-on\/advent-of-code-2020\" target=\"_blank\" rel=\"noopener\">\u6b64\u9879\u76ee<\/a>\u4e2d\u627e\u5230\u89e3\u51b3\u65b9\u6848\u3002<\/p>\n<h3>\u89e3\u51b3\u65b9\u6848<\/h3>\n<p>\u4ee5\u4e0b\u662f\u793a\u4f8b\u8f93\u5165\uff1a<\/p>\n<pre class=\"kotlin-code\" style=\"padding: 36px 0;\" data-highlight-only=\"true\">1721\n979\n366\n299\n675\n1456\n<\/pre>\n<p>\u00a0<\/p>\n<p>\u9996\u5148\uff0c\u6211\u4eec\u9700\u8981\u8bfb\u53d6\u548c\u89e3\u6790\u8f93\u5165\u3002 \u6211\u4eec\u53ef\u4ee5\u4f7f\u7528 Kotlin <code>readLines()<\/code> \u51fd\u6570\u4ece\u7ed9\u5b9a\u6587\u4ef6\u4e2d\u8bfb\u53d6\u884c\u5217\u8868\uff1a<\/p>\n<p>\u00a0<\/p>\n<pre class=\"kotlin-code\" style=\"padding: 36px 0;\" data-highlight-only=\"true\">File(\"src\/day1\/input.txt\").readLines()\n<\/pre>\n<p>\u00a0<\/p>\n<p><code>readLines()<\/code> \u8fd4\u56de\u4e00\u4e2a\u5b57\u7b26\u4e32\u5217\u8868\uff0c\u6211\u4eec\u5c06\u5176\u8f6c\u6362\u4e3a\u4e00\u4e2a\u6570\u5b57\u5217\u8868\uff1a<\/p>\n<p>\u00a0<\/p>\n<pre class=\"kotlin-code\" style=\"padding: 36px 0;\" data-highlight-only=\"true\">import java.io.File\nfun main() {\n   val numbers = File(\"src\/day1\/input.txt\")\n       .readLines()\n       .map(String::toInt)\n\n\n}\n<\/pre>\n<p>\u00a0<\/p>\n<p>\u5c06\u6b64\u4ee3\u7801\u653e\u5165 <code>main<\/code> \u51fd\u6570\u4e2d\uff0c\u8be5\u51fd\u6570\u662f\u7a0b\u5e8f\u7684\u5165\u53e3\u70b9\u3002 \u5f53\u60a8\u5f00\u59cb\u8f93\u5165\u65f6\uff0cIntelliJ IDEA \u4f1a\u81ea\u52a8\u5bfc\u5165 <code>java.io.File<\/code>\u3002<\/p>\n<p>\u73b0\u5728\uff0c\u6211\u4eec\u53ea\u9700\u8fed\u4ee3\u5217\u8868\uff0c\u7136\u540e\u5bf9\u6bcf\u4e2a\u6570\u5b57\u91cd\u590d\u8be5\u8fed\u4ee3\u5e76\u68c0\u67e5\u548c\uff1a<\/p>\n<p>\u00a0<\/p>\n<pre class=\"kotlin-code\" style=\"padding: 36px 0;\" data-highlight-only=\"true\">for (first in numbers) {\n   for (second in numbers) {\n       if (first + second == 2020) {\n           println(first * second)\n           return\n       }\n   }\n}\n<\/pre>\n<p>\u00a0<\/p>\n<p>\u5c06\u6b64\u4ee3\u7801\u653e\u5728 <code>main<\/code> \u4e2d\uff0c\u8fd9\u6837\u4e00\u6765\uff0c\u627e\u5230\u6240\u9700\u6570\u5b57\u65f6\uff0c <code>return<\/code> \u4f1a\u4ece <code>main<\/code> \u8fd4\u56de\u3002<\/p>\n<p>\u4ee5\u7c7b\u4f3c\u7684\u65b9\u5f0f\u68c0\u67e5\u4e09\u4e2a\u6570\u5b57\u7684\u548c\uff1a<\/p>\n<p>\u00a0<\/p>\n<pre class=\"kotlin-code\" style=\"padding: 36px 0;\" data-highlight-only=\"true\">for (first in numbers) {\n   for (second in numbers) {\n       for (third in numbers) {\n           if (first + second + third == 2020) {\n               println(first * second * third)\n               return\n           }\n       }\n   }\n}\n<\/pre>\n<p>\u00a0<\/p>\n<p>\u60a8\u53ef\u4ee5\u8fd0\u884c\u4e0a\u8ff0\u4ee3\u7801\u5e76\u83b7\u5f97\u7ed9\u5b9a\u8f93\u5165\u7684\u7ed3\u679c\u3002 \u5c31\u662f\u8fd9\u6837\uff01 \u7b2c\u4e00\u4e2a\u4efb\u52a1\u5176\u5b9e\u5f88\u7b80\u5355\u3002<\/p>\n<p>\u4f46\u662f\uff0c\u5bf9\u4e8e\u6bcf\u4e2a\u5143\u7d20\uff0c\u6211\u4eec\u5728\u76f8\u540c\u7684\u5217\u8868\u4e0a\u8fdb\u884c\u4e86\u53cd\u590d\u8fed\u4ee3\u3002 \u5982\u679c\u4f7f\u7528\u4e24\u4e2a\u5d4c\u5957\u5faa\u73af\u6765\u67e5\u627e\u4e24\u4e2a\u6570\u5b57\uff0c\u5219\u9700\u8981 N<sup>2<\/sup> \u6b21\u8fd0\u7b97\uff0c\u5176\u4e2d N \u662f\u5143\u7d20\u7684\u6570\u91cf\u3002 \u5f53\u6211\u4eec\u9700\u8981\u67e5\u627e\u4e09\u4e2a\u6570\u5b57\u65f6\uff0c\u5c31\u662f\u4e09\u4e2a\u5d4c\u5957\u5faa\u73af\uff0c\u4ee5\u53ca N<sup>3<\/sup> \u6b21\u8fd0\u7b97\u3002 \u5982\u679c\u6570\u5b57\u5217\u8868\u5f88\u5927\uff0c\u8fd9\u4e0d\u662f\u89e3\u51b3\u6b64\u7c7b\u95ee\u9898\u7684\u6700\u9ad8\u6548\u65b9\u5f0f\u3002 \u5f53\u7136\u8fd8\u6709\u66f4\u597d\u7684\u529e\u6cd5\uff0c\u5bf9\u5427\uff1f<\/p>\n<p>\u5f53\u7136\u6709\uff0cKotlin \u6807\u51c6\u5e93\u53ef\u4ee5\u5e2e\u52a9\u6211\u4eec\u7b80\u6d01\u5730\u8fdb\u884c\u8868\u8fbe\u3002 \u50cf\u5f80\u5e38\u4e00\u6837\uff0c\u6211\u4eec\u53ef\u4ee5\u7528\u67d0\u79cd\u7528\u4e8e\u67e5\u627e\u7ed3\u679c\u7684\u667a\u80fd\u5b58\u50a8\u6765\u4ee3\u66ff\u5197\u957f\u7684\u8ba1\u7b97\u3002<\/p>\n<h3>\u89e3\u51b3\u4e24\u4e2a\u6570\u5b57\u7684\u4efb\u52a1<\/h3>\n<p>\u9996\u5148\uff0c\u6211\u4eec\u6784\u5efa\u4e00\u4e2a\u6570\u5b57\u8865\u6570\uff08\u5373\u4e0e\u7ed9\u5b9a\u6570\u5b57\u7684\u548c\u4e3a 2020 \u7684\u6570\u5b57\uff09\u7684\u6620\u5c04\uff1a<\/p>\n<p>\u00a0<\/p>\n<pre class=\"kotlin-code\" style=\"padding: 36px 0;\" data-highlight-only=\"true\">val complements = numbers.associateBy { 2020 - it }\n<\/pre>\n<p>\u00a0<\/p>\n<p>\u6211\u4eec\u4f7f\u7528 Kotlin <code>associateBy<\/code> \u51fd\u6570\u6765\u6784\u5efa\u6620\u5c04\u3002 \u5b83\u7684 lambda \u5b9e\u53c2\u8fd4\u56de\u6b64\u6620\u5c04\u4e2d\u7684\u4e00\u4e2a\u952e\uff0c\u901a\u8fc7\u8be5\u952e\u5b58\u50a8\u5217\u8868\u5143\u7d20\u3002 \u5bf9\u4e8e\u793a\u4f8b\u8f93\u5165\uff0c\u5b83\u5c06\u662f\u4ee5\u4e0b\u6620\u5c04\uff1a<\/p>\n<p>\u00a0<\/p>\n<pre class=\"kotlin-code\" style=\"padding: 36px 0;\" data-highlight-only=\"true\">numbers: [1721, 979, 366, 299, 675, 1456]\ncomplements map: {299=1721, 1041=979, 1654=366, 1721=299, 1345=675, 564=1456}<\/pre>\n<p>\u00a0<\/p>\n<p>\u7ecf\u8fc7\u8fd9\u4e2a\u7a0b\u5e8f\uff0c\u60a8\u53ef\u4ee5\u6e05\u695a\u5730\u770b\u5230\u7b54\u6848\uff01 \u5217\u8868\u4e2d\u7684\u7b2c\u4e00\u4e2a\u6570\u5b57 <code>1721<\/code> \u4f5c\u4e3a\u952e\u51fa\u73b0\u5728 <code>complements<\/code> \u6620\u5c04\u4e2d\uff1a<code>1721=299<\/code>\uff0c\u8fd9\u610f\u5473\u7740\u5b83\u662f\u6570\u5b57 <code>299<\/code> \u7684\u8865\u6570\uff0c\u4e8c\u8005\u7684\u548c\u4e3a <code>2020<\/code>\u3002<\/p>\n<p>\u5c06\u6b64\u4fe1\u606f\u5b58\u50a8\u5728\u6620\u5c04\u4e2d\u540e\uff0c\u6211\u4eec\u53ef\u4ee5\u68c0\u67e5\u5217\u8868\u4e2d\u7684\u4efb\u4f55\u6570\u5b57\u5728\u6b64\u6620\u5c04\u4e2d\u662f\u5426\u6709\u8865\u6570\u3002 \u4ee5\u4e0b\u4ee3\u7801\u4f1a\u67e5\u627e\u7b2c\u4e00\u4e2a\u5177\u6709\u73b0\u6210\u8865\u6570\u7684\u6570\u5b57\uff1a<\/p>\n<p>\u00a0<\/p>\n<pre class=\"kotlin-code\" style=\"padding: 36px 0;\" data-highlight-only=\"true\">val pair = numbers.mapNotNull { number -&gt;\n   val complement = complements[number]\n   if (complement != null) Pair(number, complement) else null\n}.firstOrNull()\n<\/pre>\n<p>\u00a0<\/p>\n<p>\u6211\u4eec\u5c06\u6bcf\u4e2a\u6570\u5b57\u8f6c\u6362\u6210\u4e00\u4e2a\u7531\u6570\u5b57\u53ca\u5176\u8865\u6570\u7ec4\u6210\u7684\u5bf9\uff08\u5982\u679c\u8865\u6570\u5b58\u5728\uff09\uff0c\u7136\u540e\u627e\u5230\u7b2c\u4e00\u4e2a\u975e null \u7ed3\u679c\u3002<\/p>\n<p>\u6211\u4eec\u4f7f\u7528 <code>mapNotNull<\/code>\uff0c\u5b83\u4f1a\u8f6c\u6362\u5217\u8868\u4e2d\u7684\u6bcf\u4e2a\u5143\u7d20\u5e76\u7b5b\u9009\u51fa\u6240\u6709 <code>null<\/code> \u7ed3\u679c\u3002 \u5b83\u662f\u5148\u8c03\u7528 <code>map<\/code>\uff0c\u518d\u5bf9\u7ed3\u679c\u8c03\u7528 <code>filterNotNull<\/code> \u7684\u7b80\u5199\u5f62\u5f0f\u3002<\/p>\n<p><code>firstOrNull<\/code> \u4f1a\u8fd4\u56de\u5217\u8868\u4e2d\u7684\u7b2c\u4e00\u4e2a\u5143\u7d20\uff0c\u5982\u679c\u5217\u8868\u4e3a\u7a7a\uff0c\u5219\u8fd4\u56de <code>null<\/code>\u3002 Kotlin \u6807\u51c6\u5e93\u901a\u5e38\u4f7f\u7528 <code>OrNull<\/code> \u540e\u7f00\u6765\u6807\u8bb0\u5931\u8d25\u65f6\u8fd4\u56de <code>null<\/code> \u7684\u51fd\u6570\uff0c\u800c\u4e0d\u662f\u629b\u51fa\u5f02\u5e38\uff08\u5982 <code>elementAtOrNull<\/code>\u3001<code>singleOrNull<\/code> \u6216 <code>maxOrNull<\/code>\uff09\u3002<\/p>\n<p>\u4ece Kotlin 1.5.0 \u5f00\u59cb\uff0c\u60a8\u8fd8\u53ef\u4ee5\u5c06\u540e\u7eed\u7684\u4e24\u4e2a\u8fd0\u7b97 <code>mapNotNull<\/code> \u548c <code>first(OrNull)<\/code> \u66ff\u6362\u4e3a\u4e00\u4e2a\u51fd\u6570\u8c03\u7528\uff1a<code>firstNotNullOf(OrNull)<\/code>\u3002<\/p>\n<p>\u5728\u6784\u5efa\u8f85\u52a9\u7ed3\u6784\u540e\uff0c\u6211\u4eec\u8bbe\u6cd5\u901a\u8fc7 N \u6b21\u8fd0\u7b97\uff08\u800c\u4e0d\u662f\u50cf\u4e4b\u524d\u4e00\u6837\u901a\u8fc7 N<sup>2<\/sup> \u6b21\u8fd0\u7b97\uff09\u627e\u5230\u4e86\u6ee1\u8db3\u6761\u4ef6\u7684\u4e24\u4e2a\u6570\u5b57\uff01<\/p>\n<p>\u6211\u4eec\u9700\u8981\u5c06\u8fd9\u4e9b\u6570\u5b57\u76f8\u4e58\uff0c\u56e0\u6b64\u4e0b\u9762\u662f\u6700\u540e\u4e00\u6b65\uff1a<\/p>\n<p>\u00a0<\/p>\n<pre class=\"kotlin-code\" style=\"padding: 36px 0;\" data-highlight-only=\"true\">println(pair?.let { (a, b) -&gt; a * b })\n<\/pre>\n<p>\u00a0<\/p>\n<p><code>pair<\/code> \u53d8\u91cf\u5305\u542b\u7531\u4e24\u4e2a\u6570\u5b57\u7ec4\u6210\u7684\u53ef\u4ee5\u4e3a null \u7684 <code>Pair<\/code>\uff0c\u5982\u679c\u521d\u59cb\u5217\u8868\u4e0d\u5305\u542b\u548c\u4e3a 2020 \u7684\u6570\u5b57\uff0c\u5219\u4e3a <code>null<\/code>\u3002 \u6211\u4eec\u4f7f\u7528\u5b89\u5168\u8bbf\u95ee <code>?.<\/code> \u548c <code>let<\/code> \u51fd\u6570\u5e76\u5728 lambda \u8bed\u6cd5\u4e2d\u8fdb\u884c\u6790\u6784\uff0c\u5728 <code>pair<\/code> \u4e0d\u4e3a <code>null<\/code> \u7684\u60c5\u51b5\u4e0b\u663e\u793a\u7ed3\u679c\u3002<\/p>\n<h3>\u89e3\u51b3\u4e09\u4e2a\u6570\u5b57\u7684\u4efb\u52a1<\/h3>\n<p>\u4e0b\u4e00\u6b65\u662f\u89e3\u51b3\u4e09\u4e2a\u6570\u5b57\u7684\u95ee\u9898\u3002 \u6211\u4eec\u6765\u91cd\u7528\u76ee\u524d\u4e3a\u6b62\u6240\u505a\u7684\u5de5\u4f5c\uff0c\u5e76\u5c06\u67e5\u627e\u548c\u4e3a\u7ed9\u5b9a\u6570\u5b57\u7684\u4e00\u5bf9\u6570\u5b57\u7684\u903b\u8f91\u63d0\u53d6\u5230\u4e00\u4e2a\u5355\u72ec\u7684\u51fd\u6570\u4e2d\uff1a<\/p>\n<p>\u00a0<\/p>\n<pre class=\"kotlin-code\" style=\"padding: 36px 0;\" data-highlight-only=\"true\">fun List&lt;Int&gt;.findPairOfSum(sum: Int): Pair&lt;Int, Int&gt;? {\n   \/\/ Map: sum - x -&gt; x\n   val complements = associateBy { sum - it }\n   return firstNotNullOfOrNull { number -&gt;\n       val complement = complements[number]\n       if (complement != null) Pair(number, complement) else null\n   }\n}\n<\/pre>\n<p>\u00a0<\/p>\n<p>\u6211\u4eec\u8fd8\u4f7f\u7528\u4e86 <code>firstNotNullOfOrNull<\/code> \u51fd\u6570\u3002<\/p>\n<p>\u63a5\u4e0b\u6765\uff0c\u6211\u4eec\u4f7f\u7528 <code>findPairOfSum<\/code> \u6784\u5efa\u4e00\u4e2a\u8f85\u52a9\u6620\u5c04\uff0c\u7528\u6765\u5b58\u50a8\u6bcf\u4e2a\u6570\u5b57\u7684\u8865<em>\u503c\u5bf9<\/em>\uff0c\u8fd9\u4e9b\u503c\u4e0e\u6b64\u6570\u5b57\u7684\u548c\u4e3a 2020\uff1a<\/p>\n<p>\u00a0<\/p>\n<pre class=\"kotlin-code\" style=\"padding: 36px 0;\" data-highlight-only=\"true\">\/\/ Map: x -&gt; (y, z) where y + z = 2020 - x\nval complementPairs: Map&lt;Int, Pair&lt;Int, Int&gt;?&gt; =\n   numbers.associateWith { numbers.findPairOfSum(2020 - it) }\n<\/pre>\n<p>\u00a0<\/p>\n<p>\u5bf9\u4e8e\u76f8\u540c\u7684\u521d\u59cb\u8f93\u5165\uff0c\u4e0b\u9762\u662f\u8865\u6570\u5bf9\u6620\u5c04\uff1a<\/p>\n<p>\u00a0<\/p>\n<pre class=\"kotlin-code\" style=\"padding: 36px 0;\" data-highlight-only=\"true\">numbers: [1721, 979, 366, 299, 675, 1456]\ncomplement pairs: {1721=null, 979=(366, 675), 366=(979, 675), 299=null, 675=(979, 366), 1456=null}<\/pre>\n<p>\u00a0<\/p>\n<p>\u548c\u4e4b\u524d\u4e00\u6837\uff0c\u60a8\u5df2\u7ecf\u53ef\u4ee5\u770b\u5230\u7b54\u6848\u4e86\uff01 \u5b83\u662f\u4e0e\u6620\u5c04\u4e2d\u975e null \u5bf9\u76f8\u5bf9\u5e94\u7684\u6570\u5b57\u3002<\/p>\n<p>\u7136\u800c\uff0c\u6211\u4eec\u5e76\u4e0d\u771f\u7684\u9700\u8981\u6784\u5efa\u6574\u4e2a\u6620\u5c04\u3002\u6211\u4eec\u53ea\u9700\u8981\u627e\u5230\u5bf9\u5e94\u4e8e\u975e null \u5bf9\u7684\u7b2c\u4e00\u4e2a\u6570\u5b57\uff01 \u6211\u4eec\u4f7f\u7528\u5df2\u7ecf\u719f\u6089\u7684 <code>firstNotNullOfOrNull<\/code> \u51fd\u6570\u8fdb\u884c\u67e5\u627e\uff1a<\/p>\n<p>\u00a0<\/p>\n<pre class=\"kotlin-code\" style=\"padding: 36px 0;\" data-highlight-only=\"true\">fun List&lt;Int&gt;.findTripleOfSum(): Triple&lt;Int, Int, Int&gt;? =\n   firstNotNullOfOrNull { x -&gt;\n       findPairOfSum(2020 - x)?.let { pair -&gt;\n           Triple(x, pair.first, pair.second)\n       }\n   }\n<\/pre>\n<p>\u00a0<\/p>\n<p>\u8bf7\u6ce8\u610f Kotlin \u7684\u7b80\u660e\u8bed\u6cd5\uff0c\u8be5\u51fd\u6570\u53ef\u4ee5\u76f4\u63a5\u8fd4\u56de\u4e00\u4e2a\u8868\u8fbe\u5f0f\u3002<\/p>\n<p>\u5982\u679c\u5f97\u5230\u7684\u4e09\u5143\u7ec4\u4e0d\u4e3a null\uff0c\u5219\u6700\u540e\u4e00\u6b65\u662f\u8ba1\u7b97\u4e58\u79ef\uff0c\u8fd9\u4e0e\u6211\u4eec\u4e4b\u524d\u7684\u65b9\u5f0f\u7c7b\u4f3c\uff1a<\/p>\n<p>\u00a0<\/p>\n<pre class=\"kotlin-code\" style=\"padding: 36px 0;\" data-highlight-only=\"true\">println(triple?.let { (x, y, z) -&gt; x * y * z} )\n<\/pre>\n<p>\u00a0<\/p>\n<p>\u8fd9\u90e8\u5206\u5230\u6b64\u7ed3\u675f\uff01<\/p>\n<p>\u5728\u4e0b\u4e00\u90e8\u5206\u4e2d\uff0c\u6211\u4eec\u5c06\u8ba8\u8bba\u5982\u4f55\u89e3\u51b3\u7b2c\u4e8c\u4e2a\u4efb\u52a1\u3002 \u5982\u679c\u60a8\u89c9\u5f97\u6b64\u5185\u5bb9\u6709\u7528\uff0c\u5e76\u5e0c\u671b\u6211\u4eec\u4e3a\u66f4\u591a\u4efb\u52a1\u63d0\u4f9b\u89e3\u51b3\u65b9\u6848\uff0c\u8bf7\u544a\u8bc9\u6211\u4eec\uff01<\/p>\n<p>\u2014<\/p>\n<p>*\u7ecf <a href=\"https:\/\/adventofcode.com\/\" target=\"_blank\" rel=\"noopener\">Advent of Code<\/a> (<a href=\"https:\/\/twitter.com\/ericwastl\" target=\"_blank\" rel=\"noopener\">Eric Wastl<\/a>) \u8bb8\u53ef\u4f7f\u7528\u3002<\/p>\n\n\n<p><\/p>\n\n\n\n<p>\u672c\u535a\u6587\u82f1\u6587\u539f\u4f5c\u8005\uff1a<\/p>\n\n\n    <div class=\"about-author \">\n        <div class=\"about-author__box\">\n            <div class=\"row\">\n                <div class=\"about-author__box-img\">\n                    <img decoding=\"async\" src=\"https:\/\/secure.gravatar.com\/avatar\/?s=200&#038;r=g\" width=\"200\" height=\"200\" alt=\"\" loading=\"lazy\"  class=\"avatar avatar-200 wp-user-avatar wp-user-avatar-200 photo avatar-default\">\n                <\/div>\n                <div class=\"about-author__box-text\">\n                                                        <\/div>\n            <\/div>\n        <\/div>\n    <\/div>\n","protected":false},"author":1297,"featured_media":162250,"comment_status":"open","ping_status":"closed","template":"","categories":[89],"tags":[63,91,3682],"cross-post-tag":[],"acf":[],"_links":{"self":[{"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/kotlin\/300105"}],"collection":[{"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/kotlin"}],"about":[{"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/types\/kotlin"}],"author":[{"embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/users\/1297"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/comments?post=300105"}],"version-history":[{"count":2,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/kotlin\/300105\/revisions"}],"predecessor-version":[{"id":300115,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/kotlin\/300105\/revisions\/300115"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/media\/162250"}],"wp:attachment":[{"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/media?parent=300105"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/categories?post=300105"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/tags?post=300105"},{"taxonomy":"cross-post-tag","embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/cross-post-tag?post=300105"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}