{"id":963,"date":"2025-12-14T22:00:13","date_gmt":"2025-12-14T14:00:13","guid":{"rendered":"https:\/\/www.guanhaobo.cn\/?p=963"},"modified":"2025-12-14T22:00:13","modified_gmt":"2025-12-14T14:00:13","slug":"leetcode-207-%e8%af%be%e7%a8%8b%e8%a1%a8","status":"publish","type":"post","link":"https:\/\/www.guanhaobo.cn\/?p=963","title":{"rendered":"LeetCode 207 – \u8bfe\u7a0b\u8868"},"content":{"rendered":"

\u9898\u76ee\u63cf\u8ff0<\/h1>\n

\u4f60\u8fd9\u4e2a\u5b66\u671f\u5fc5\u987b\u9009\u4fee numCourses \u95e8\u8bfe\u7a0b\uff0c\u8bb0\u4e3a 0 \u5230 numCourses – 1 \u3002<\/p>\n

\u5728\u9009\u4fee\u67d0\u4e9b\u8bfe\u7a0b\u4e4b\u524d\u9700\u8981\u4e00\u4e9b\u5148\u4fee\u8bfe\u7a0b\u3002 \u5148\u4fee\u8bfe\u7a0b\u6309\u6570\u7ec4 prerequisites \u7ed9\u51fa\uff0c\u5176\u4e2d prerequisites[i] = [ai, bi] \uff0c\u8868\u793a\u5982\u679c\u8981\u5b66\u4e60\u8bfe\u7a0b ai \u5219 \u5fc5\u987b \u5148\u5b66\u4e60\u8bfe\u7a0b bi \u3002<\/p>\n

\u4f8b\u5982\uff0c\u5148\u4fee\u8bfe\u7a0b\u5bf9 [0, 1] \u8868\u793a\uff1a\u60f3\u8981\u5b66\u4e60\u8bfe\u7a0b 0 \uff0c\u4f60\u9700\u8981\u5148\u5b8c\u6210\u8bfe\u7a0b 1 \u3002
\n\u8bf7\u4f60\u5224\u65ad\u662f\u5426\u53ef\u80fd\u5b8c\u6210\u6240\u6709\u8bfe\u7a0b\u7684\u5b66\u4e60\uff1f\u5982\u679c\u53ef\u4ee5\uff0c\u8fd4\u56de true \uff1b\u5426\u5219\uff0c\u8fd4\u56de false \u3002<\/p>\n

\u9898\u76ee\u5206\u6790<\/h1>\n

\u8bb0\u5f55\u6bcf\u4e2a\u70b9\u7684\u5165\u5ea6\uff0c\u53ca\u540e\u7eed\u7684\u70b9\uff08\u90bb\u63a5\u8868\uff09
\nBFS\uff0c\u4ece\u5165\u5ea6\u4e3a 0 \u7684\u70b9\u5f00\u59cb
\n\u6bcf\u8bbf\u95ee\u4e00\u4e2a\u70b9\uff0c\u5c06\u540e\u7eed\u70b9\u7684\u5165\u5ea6\u51cf1\uff0c\u7136\u540e\u5c06\u5176\u4e2d\u5165\u5ea6\u4e3a0\u7684\u5165\u961f
\n\u6700\u540e\u68c0\u67e5\u4e00\u904d\u662f\u5426\u5b58\u5728\u5165\u5ea6 > 0 \u7684\u70b9<\/p>\n

Java<\/h1>\n
public boolean canFinish(int numCourses, int[][] prerequisites) {\n    int[] pre = new int[numCourses];\n    List<List<Integer>> next = new ArrayList<>();\n    Queue<Integer> queue = new LinkedList<>();\n    for (int i = 0; i < numCourses; i++) {\n        next.add(new ArrayList<>());\n    }\n    for (int[] pair : prerequisites) {\n        pre[pair[0]]++;\n        next.get(pair[1]).add(pair[0]);\n    }\n    for (int i = 0; i < numCourses; i++) {\n        if (pre[i] == 0) {\n            queue.offer(i);\n        }\n    }\n    while (!queue.isEmpty()) {\n        Integer x = queue.poll();\n        List<Integer> list = next.get(x);\n        for (Integer i : list) {\n            pre[i]--;\n            if (pre[i] == 0) {\n                queue.offer(i);\n            }\n        }\n    }\n    for (int i = 0; i < numCourses; i++) {\n        if (pre[i] > 0) {\n            return false;\n        }\n    }\n    return true;\n}\n<\/code><\/pre>\n
Kotlin<\/h1>\n
fun canFinish(numCourses: Int, prerequisites: Array<IntArray>): Boolean {\n    val pre = IntArray(numCourses)\n    val next = Array(numCourses) { ArrayList<Int>() }\n    val queue = LinkedList<Int>()\n    for (array in prerequisites) {\n        pre[array[0]]++\n        next[array[1]].add(array[0])\n    }\n    for (i in 0 until numCourses) {\n        if (pre[i] == 0) {\n            queue.offer(i)\n        }\n    }\n\n    while (!queue.isEmpty()) {\n        val num = queue.poll()\n\n        for (i in next[num]) {\n            pre[i]--\n            if (pre[i] == 0) {\n                queue.offer(i)\n            }\n        }\n    }\n\n    for (i in 0 until numCourses) {\n        if (pre[i] > 0) {\n            return false\n        }\n    }\n    return true\n}\n<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"
\u9898\u76ee\u63cf\u8ff0 \u4f60\u8fd9\u4e2a\u5b66\u671f\u5fc5\u987b\u9009\u4fee numCourses \u95e8\u8bfe\u7a0b\uff0c\u8bb0\u4e3a 0 \u5230 numCourses – […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[88,20,43],"class_list":["post-963","post","type-post","status-publish","format-standard","hentry","category-algo","tag-bfs","tag-leetcode","tag-43"],"_links":{"self":[{"href":"https:\/\/www.guanhaobo.cn\/index.php?rest_route=\/wp\/v2\/posts\/963","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.guanhaobo.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.guanhaobo.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.guanhaobo.cn\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.guanhaobo.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=963"}],"version-history":[{"count":1,"href":"https:\/\/www.guanhaobo.cn\/index.php?rest_route=\/wp\/v2\/posts\/963\/revisions"}],"predecessor-version":[{"id":964,"href":"https:\/\/www.guanhaobo.cn\/index.php?rest_route=\/wp\/v2\/posts\/963\/revisions\/964"}],"wp:attachment":[{"href":"https:\/\/www.guanhaobo.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=963"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.guanhaobo.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=963"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.guanhaobo.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=963"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}