{"id":617,"date":"2020-09-26T11:03:48","date_gmt":"2020-09-26T03:03:48","guid":{"rendered":"http:\/\/39.96.58.60\/?p=617"},"modified":"2022-10-18T16:45:04","modified_gmt":"2022-10-18T08:45:04","slug":"leetcode-685-%e5%86%97%e4%bd%99%e8%bf%9e%e6%8e%a5-ii","status":"publish","type":"post","link":"http:\/\/www.yatenglg.cn\/blog\/?p=617","title":{"rendered":"Leetcode 685. \u5197\u4f59\u8fde\u63a5 II"},"content":{"rendered":"<p>\u5728\u672c\u95ee\u9898\u4e2d\uff0c\u6709\u6839\u6811\u6307\u6ee1\u8db3\u4ee5\u4e0b\u6761\u4ef6\u7684<strong>\u6709\u5411<\/strong>\u56fe\u3002\u8be5\u6811\u53ea\u6709\u4e00\u4e2a\u6839\u8282\u70b9\uff0c\u6240\u6709\u5176\u4ed6\u8282\u70b9\u90fd\u662f\u8be5\u6839\u8282\u70b9\u7684\u540e\u7ee7\u3002\u6bcf\u4e00\u4e2a\u8282\u70b9\u53ea\u6709\u4e00\u4e2a\u7236\u8282\u70b9\uff0c\u9664\u4e86\u6839\u8282\u70b9\u6ca1\u6709\u7236\u8282\u70b9\u3002<\/p>\n<p>\u8f93\u5165\u4e00\u4e2a\u6709\u5411\u56fe\uff0c\u8be5\u56fe\u7531\u4e00\u4e2a\u6709\u7740N\u4e2a\u8282\u70b9 (\u8282\u70b9\u503c\u4e0d\u91cd\u590d1, 2, &#8230;, N) \u7684\u6811\u53ca\u4e00\u6761\u9644\u52a0\u7684\u8fb9\u6784\u6210\u3002\u9644\u52a0\u7684\u8fb9\u7684\u4e24\u4e2a\u9876\u70b9\u5305\u542b\u57281\u5230N\u4e2d\u95f4\uff0c\u8fd9\u6761\u9644\u52a0\u7684\u8fb9\u4e0d\u5c5e\u4e8e\u6811\u4e2d\u5df2\u5b58\u5728\u7684\u8fb9\u3002<\/p>\n<p>\u7ed3\u679c\u56fe\u662f\u4e00\u4e2a\u4ee5<code>\u8fb9<\/code>\u7ec4\u6210\u7684\u4e8c\u7ef4\u6570\u7ec4\u3002 \u6bcf\u4e00\u4e2a<code>\u8fb9<\/code> \u7684\u5143\u7d20\u662f\u4e00\u5bf9 <code>[u, v]<\/code>\uff0c\u7528\u4ee5\u8868\u793a<strong>\u6709\u5411<\/strong>\u56fe\u4e2d\u8fde\u63a5\u9876\u70b9 <code>u<\/code> \u548c\u9876\u70b9 <code>v<\/code> \u7684\u8fb9\uff0c\u5176\u4e2d <code>u<\/code> \u662f <code>v<\/code> \u7684\u4e00\u4e2a\u7236\u8282\u70b9\u3002<\/p>\n<p>\u8fd4\u56de\u4e00\u6761\u80fd\u5220\u9664\u7684\u8fb9\uff0c\u4f7f\u5f97\u5269\u4e0b\u7684\u56fe\u662f\u6709N\u4e2a\u8282\u70b9\u7684\u6709\u6839\u6811\u3002\u82e5\u6709\u591a\u4e2a\u7b54\u6848\uff0c\u8fd4\u56de\u6700\u540e\u51fa\u73b0\u5728\u7ed9\u5b9a\u4e8c\u7ef4\u6570\u7ec4\u7684\u7b54\u6848\u3002<\/p>\n<p><strong>\u793a\u4f8b\u00a01:<\/strong><\/p>\n<pre><strong>\u8f93\u5165:<\/strong> [[1,2], [1,3], [2,3]]\n\n<strong>\u8f93\u51fa:<\/strong> [2,3]\n\n<strong>\u89e3\u91ca:<\/strong> \u7ed9\u5b9a\u7684\u6709\u5411\u56fe\u5982\u4e0b:\n\n  1\n\n \/ \\\n\nv   v\n\n2--&gt;3\n\n<\/pre>\n<p><strong>\u793a\u4f8b 2:<\/strong><\/p>\n<pre><strong>\u8f93\u5165:<\/strong> [[1,2], [2,3], [3,4], [4,1], [1,5]]\n\n<strong>\u8f93\u51fa:<\/strong> [4,1]\n\n<strong>\u89e3\u91ca:<\/strong> \u7ed9\u5b9a\u7684\u6709\u5411\u56fe\u5982\u4e0b:\n\n5 &lt;- 1 -&gt; 2\n\n     ^    |\n\n     |    v\n\n     4 &lt;- 3\n\n<\/pre>\n<p><strong>\u6ce8\u610f:<\/strong><\/p>\n<ul>\n<li>\u4e8c\u7ef4\u6570\u7ec4\u5927\u5c0f\u7684\u57283\u52301000\u8303\u56f4\u5185\u3002<\/li>\n<li>\u4e8c\u7ef4\u6570\u7ec4\u4e2d\u7684\u6bcf\u4e2a\u6574\u6570\u57281\u5230N\u4e4b\u95f4\uff0c\u5176\u4e2d N \u662f\u4e8c\u7ef4\u6570\u7ec4\u7684\u5927\u5c0f\u3002<\/li>\n<\/ul>\n<p>**\u96be\u5ea6**: Hard<\/p>\n<p>**\u6807\u7b7e**: \u6811\u3001 \u6df1\u5ea6\u4f18\u5148\u641c\u7d22\u3001 \u5e76\u67e5\u96c6\u3001 \u56fe\u3001<\/p>\n<div class=\"hcb_wrap\">\n<pre class=\"prism undefined-numbers lang-python\" data-lang=\"Python\"><code>\n# -*- coding: utf-8 -*-\n# @Author  : LG\n\n\"\"\"\n\u6267\u884c\u7528\u65f6\uff1a116 ms, \u5728\u6240\u6709 Python3 \u63d0\u4ea4\u4e2d\u51fb\u8d25\u4e868.59% \u7684\u7528\u6237\n\u5185\u5b58\u6d88\u8017\uff1a18.3 MB, \u5728\u6240\u6709 Python3 \u63d0\u4ea4\u4e2d\u51fb\u8d25\u4e865.71% \u7684\u7528\u6237\n\n\u89e3\u9898\u601d\u8def\uff1a\n    1.  [1,2], [2,3], [3,1]     # \u6210\u73af\n    1.1     [1,2], [2,3], [3,1], [4,1]  # \u6210\u73af\uff0c\u4e14\u6709\u5165\u5ea6\u5927\u4e8e1\u7684\u70b9(\u4ec5\u53ef\u6709\u4e00\u4e2a)\n    1.2     [1,2], [2,3], [3,1], [1,4]  # \u6210\u73af\uff0c\u4e14\u6709\u5206\u652f\n    2.  [1,2], [2,3], [1,3]     # \u4e0d\u6210\u73af\uff0c \u5165\u5ea6\u5927\u4e8e1\n    1.1     [1,2], [2,3], [1,3], [4,1]  # \u4e0d\u6210\u73af\uff0c\u5165\u5ea6\u5927\u4e8e1\uff0c\u5165\u5206\u652f\n    1.2     [1,2], [2,3], [1,3], [1,4]  # \u4e0d\u6210\u73af\uff0c\u5165\u5ea6\u5927\u4e8e1\uff0c\u51fa\u5206\u652f\n\n    \u7ecf\u8fc7\u6574\u5408\uff0c\u53ef\u6574\u5408\u4e3a\u4e24\u79cd\u60c5\u51b5:\n        1. \u5b58\u5728\u5165\u5ea6\u5927\u4e8e1 \u7684\u70b9\uff0c\u591a\u4f59\u7684\u8fb9\u5fc5\u5b9a\u662f\u5165\u5ea6\u5927\u4e8e1\u7684\u8fb9\uff0c\n            1.1 \u82e5\u6210\u73af\uff0c\u5219\u5220\u9664\u6210\u73af\u7684\u90a3\u6761\u5165\u5ea6\u5927\u4e8e1\u7684\u8fb9\n            1.2 \u82e5\u4e0d\u6210\u73af\uff0c\u5220\u9664\u6700\u540e\u6dfb\u52a0\u7684\u90a3\u6761\u5165\u5ea6\u5927\u4e8e1\u7684\u8fb9\n        2. \u4e0d\u5b58\u5728\u5165\u5ea6\u5927\u4e8e1 \u7684\u70b9\uff0c\u5219\u5fc5\u7136\u6709\u73af\n            \u5220\u9664\u6700\u540e\u6dfb\u52a0\u7684\u73af\u4e2d\u7684\u8fb9\n\n\"\"\"\nclass Solution:\n    def findRedundantDirectedConnection(self, edges: List[List[int]]) -&gt; List[int]:\n\n        def is_cycle(start, used, to_dict): # \u8d77\u59cb\u70b9\uff0c\u5f53\u524d\u901a\u8fc7\u7684\u8def\u5f84\uff0c\u8def\u5f84\u5b57\u5178\n            # print(start, used, to_dict)\n            if start not in used:   # \u5982\u679c\u5f53\u524d\u8d77\u59cb\u70b9\u6ca1\u6709\u7ecf\u8fc7\uff0c\u5219\u4e0d\u6210\u73af\n                nexts = to_dict[start]  # \u5f53\u524d\u8d77\u59cb\u70b9\u53ef\u4ee5\u53bb\u7684\u8282\u70b9\n                if nexts != []:\n                    next = nexts[-1]    # \u53d6\u6700\u540e\u4e00\u4e2a\u53ef\u4ee5\u53bb\u7684\u8282\u70b9\n                    to_dict[start].pop(-1)  # \u5220\u9664\u53d6\u8fc7\u7684\u8def\u5f84\n                    if is_cycle(next, used+[start], to_dict):   # \u627e\u4e0b\u4e00\u4e2a\u8def\u5f84\n                        return True\n                else:\n                    return\n            else:\n                for i ,e in enumerate(used):    # \u5f53\u524d\u8def\u5f84\u6210\u73af\uff0c\u4f46\u4e0d\u4e00\u5b9a\u53ea\u6709\u73af\uff0c\u8fd9\u91cc\u5c06\u5bf9\u4e8e\u7684\u8282\u70b9\u5220\u6389\n                    if e == start:\n                        self.circle = used[i:] + [start]\n                        break\n                return True\n\n        self.circle = []    # \u7528\u4e8e\u8bb0\u5f55\u73af\n        to_dict = defaultdict(list) # \u8def\u5f84\u5b57\u5178\n        to_list = []\n        to_ = None\n\n        for edge in edges:\n            to_dict[edge[0]].append(edge[1])\n            if edge[1] not in to_list:\n                to_list.append(edge[1])\n            else:\n                to_ = edge[1]   # \u5165\u5ea6\u7b49\u4e8e2\u7684\u70b9\n\n\n        if to_ is None: # \u6ca1\u6709\u5165\u5ea6\u5927\u4e8e1\u7684\u70b9, \u5fc5\u6709\u73af\uff0c\u627e\u73af\n            for edge in edges[::-1]:    # \u56e0\u4e3a\u9700\u8981\u5220\u9664\u6700\u540e\u51fa\u73b0\u5728\u6570\u7ec4\u4e2d\u7684\u7b54\u6848\uff0c\u8fd9\u91cc\u53cd\u5e8f\u68c0\u67e5\u3002\n                start = edge[0]\n                if is_cycle(start, [], to_dict):  # \u627e\u73af\n                    self.circle = [[self.circle[i], self.circle[i+1]] for i in range(len(self.circle)-1)]\n                    return self.circle[0]\n\n        else:   # \u5b58\u5728\u5165\u5ea6\u5927\u4e8e1\u7684\u70b9\uff0c\u5728\u672c\u9898\u4e2d\u53ea\u53ef\u80fd\u5b58\u5728\u4e00\u4e2a,\u4e14\u5165\u5ea6\u4e3a2\n            tos_ = []   # \u4fdd\u5b58\u5165\u5ea6\u4e3a2 \u7684\u4e24\u6761\u8def\u5f84\n            for edge in edges[::-1]:    # \u627e\u73af,\u6b64\u65f6\u53ea\u9700\u627e\u5165\u5ea6\u4e3a2\u7684\u70b9\u662f\u5426\u5b58\u5728\u73af\u5373\u53ef\n                if edge[-1] == to_:\n                    tos_.append(edge)\n                    if self.circle == []: # \u6ca1\u627e\u5230\u73af\u65f6\uff0c\u7ee7\u7eed\u627e\uff0c\u627e\u5230\u5c31\u4e0d\u9700\u8981\u4e86\n                        if is_cycle(edge[0], [], to_dict):\n                            self.circle = [[self.circle[i], self.circle[i + 1]] for i in range(len(self.circle)-1)]\n\n            for t in tos_[::-1]:\n                if t in self.circle:\n                    return t\n            return tos_[0]\n\n<\/code><\/pre>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>\u5728\u672c\u95ee\u9898\u4e2d\uff0c\u6709\u6839\u6811\u6307\u6ee1\u8db3\u4ee5\u4e0b\u6761\u4ef6\u7684\u6709\u5411\u56fe\u3002\u8be5\u6811\u53ea\u6709\u4e00\u4e2a\u6839\u8282\u70b9\uff0c\u6240\u6709\u5176\u4ed6\u8282\u70b9\u90fd\u662f\u8be5\u6839\u8282\u70b9\u7684\u540e\u7ee7\u3002\u6bcf\u4e00\u4e2a\u8282\u70b9\u53ea\u6709\u4e00&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":[],"categories":[11,1],"tags":[],"_links":{"self":[{"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=\/wp\/v2\/posts\/617"}],"collection":[{"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=617"}],"version-history":[{"count":2,"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=\/wp\/v2\/posts\/617\/revisions"}],"predecessor-version":[{"id":758,"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=\/wp\/v2\/posts\/617\/revisions\/758"}],"wp:attachment":[{"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=617"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=617"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=617"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}