{"id":7517,"date":"2026-07-27T23:14:13","date_gmt":"2026-07-27T15:14:13","guid":{"rendered":"https:\/\/i007.cc\/wordpress\/?p=7517"},"modified":"2026-07-27T23:14:13","modified_gmt":"2026-07-27T15:14:13","slug":"%e7%94%a8c%e8%ae%b2%e8%ae%b2-%e9%9d%92%e8%9b%99%e8%b7%b3%ef%bc%88leetcode-403%ef%bc%89%e7%9a%84%e6%9c%80%e4%bd%b3%e6%80%9d%e8%b7%af","status":"publish","type":"post","link":"https:\/\/i007.cc\/wordpress\/archives\/7517","title":{"rendered":"\u7528C++\u8bb2\u8bb2 \u9752\u86d9\u8df3\uff08LeetCode 403\uff09\u7684\u6700\u4f73\u601d\u8def"},"content":{"rendered":"
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LeetCode 403 \u9752\u86d9\u8df3\u77f3\u5934\uff0c\u672c\u8d28\u662f\u4e00\u4e2a\u300c\u8bb0\u5fc6\u5316\u641c\u7d22\/\u52a8\u6001\u89c4\u5212\u300d\u95ee\u9898\uff0c\u800c\u4e0d\u662f\u5355\u7eaf\u7684\u8d2a\u5fc3\u6216\u4e8c\u5206\u80fd\u76f4\u63a5\u89e3\u51b3\u7684\uff0c\u539f\u56e0\u662f\u6bcf\u4e00\u6b65\u8df3\u8dc3\u7684\u6b65\u957f\u53ef\u4ee5\u6bd4\u4e0a\u4e00\u6b65\u5927 1\u3001\u76f8\u7b49\u3001\u6216\u5c0f 1\uff0c\u6b65\u957f\u65e2\u80fd\u589e\u5927\u4e5f\u80fd\u51cf\u5c0f\uff0c\u72b6\u6001\u91cc\u65e2\u8981\u8bb0\u5f55\u300c\u5728\u54ea\u5757\u77f3\u5934\u4e0a\u300d\uff0c\u53c8\u8981\u8bb0\u5f55\u300c\u4e0a\u4e00\u6b65\u8df3\u4e86\u591a\u8fdc\u300d\uff0c\u8fd9\u4e24\u4e2a\u7ef4\u5ea6\u5408\u5728\u4e00\u8d77\u624d\u80fd\u5224\u65ad\u9752\u86d9\u662f\u5426\u6709\u4e00\u6761\u5408\u6cd5\u8def\u5f84\u8df3\u5230\u7ec8\u70b9\u3002<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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\u6700\u4f73\u601d\u8def\u662f\uff1a\u4e3a\u6bcf\u5757\u77f3\u5934\u7ef4\u62a4\u4e00\u4e2a\u96c6\u5408\uff0c\u8bb0\u5f55\u300c\u6240\u6709\u80fd\u8df3\u5230\u8fd9\u5757\u77f3\u5934\u4e0a\u7684\u5408\u6cd5\u4e0a\u4e00\u6b65\u6b65\u957f k\u300d\uff1b\u4ece\u7b2c\u4e00\u5757\u77f3\u5934\uff08\u6b65\u957f\u4e3a 0\uff09\u51fa\u53d1\uff0c\u4f9d\u6b21\u5904\u7406\u6bcf\u5757\u77f3\u5934\u80fd\u5230\u8fbe\u7684\u4e0b\u4e00\u5757\u77f3\u5934\uff0c\u628a\u65b0\u7684\u6b65\u957f\u8bb0\u5f55\u5230\u76ee\u6807\u77f3\u5934\u7684\u96c6\u5408\u91cc\uff1b\u6700\u540e\u770b\u7ec8\u70b9\u77f3\u5934\u7684\u96c6\u5408\u662f\u5426\u975e\u7a7a\u3002<\/p>\n

\u7528 index \u800c\u4e0d\u662f\u77f3\u5934\u7684\u5750\u6807\u503c\u4f5c\u4e3a dp \u6570\u7ec4\u4e0b\u6807\u4f1a\u66f4\u9ad8\u6548\uff0c\u56e0\u4e3a\u53ef\u4ee5\u907f\u514d\u6bcf\u6b21\u90fd\u7528\u5750\u6807\u53bb\u54c8\u5e0c\u67e5\u627e\uff1a<\/p>\n

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class Solution {\r\npublic:\r\n    bool canCross(vector<int>& stones) {\r\n        int n = stones.size();\r\n        if (n == 1) return true; \/\/ \u53ea\u6709\u4e00\u5757\u77f3\u5934\uff0c\u9752\u86d9\u5df2\u7ecf\u5728\u7ec8\u70b9\r\n\r\n        unordered_map<int, int> indexOf; \/\/ \u77f3\u5934\u5750\u6807 -> \u4e0b\u6807\r\n        for (int i = 0; i < n; ++i) indexOf[stones[i]] = i;\r\n\r\n        vector<unordered_set<int>> dp(n); \/\/ dp[i] = \u6240\u6709\u80fd\u5230\u8fbe\u7b2c i \u5757\u77f3\u5934\u7684\u6b65\u957f\u96c6\u5408\r\n        dp[0].insert(0);\r\n\r\n        for (int i = 0; i < n; ++i) {\r\n            for (int k : dp[i]) {\r\n                for (int step = k - 1; step <= k + 1; ++step) {\r\n                    if (step <= 0) continue; \/\/ \u6b65\u957f\u5fc5\u987b\u4e3a\u6b63\r\n                    int nextPos = stones[i] + step;\r\n                    auto it = indexOf.find(nextPos);\r\n                    if (it != indexOf.end() && it->second > i) {\r\n                        dp[it->second].insert(step);\r\n                    }\r\n                }\r\n            }\r\n        }\r\n\r\n        return !dp[n - 1].empty();\r\n    }\r\n};<\/pre>\n
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\u51e0\u4e2a\u8bbe\u8ba1\u4e0a\u7684\u5173\u952e\u70b9\uff1a<\/p>\n
\u7528 vector<unordered_set<int>> \u800c\u4e0d\u662f\u5355\u7eaf\u7684 vector<bool>\uff0c\u662f\u56e0\u4e3a\u300c\u80fd\u5426\u5230\u8fbe\u67d0\u5757\u77f3\u5934\u300d\u4e0d\u591f\uff0c\u8fd8\u9700\u8981\u77e5\u9053\u300c\u7528\u4ec0\u4e48\u6b65\u957f\u5230\u8fbe\u7684\u300d\uff0c\u624d\u80fd\u63a8\u51fa\u4e0b\u4e00\u6b65\u53ef\u4ee5\u8df3\u591a\u8fdc\uff0c\u8fd9\u662f\u8fd9\u9053\u9898\u548c\u666e\u901a\u53ef\u8fbe\u6027 DP \u6700\u5927\u7684\u533a\u522b\u3002<\/p>\n
\u5916\u5c42\u6309\u77f3\u5934\u4e0b\u6807\u4ece\u5c0f\u5230\u5927\u904d\u5386\uff0c\u4fdd\u8bc1\u5904\u7406\u7b2c i \u5757\u77f3\u5934\u65f6\uff0c\u6240\u6709\u80fd\u5230\u8fbe\u5b83\u7684\u8def\u5f84\u90fd\u5df2\u7ecf\u88ab\u8bb0\u5f55\u8fdb dp[i] \u4e86\uff08\u56e0\u4e3a\u5750\u6807\u9012\u589e\uff0c\u80fd\u5230\u8fbe i \u7684\u77f3\u5934\u4e0b\u6807\u4e00\u5b9a\u5c0f\u4e8e i\uff09\uff0c\u8fd9\u662f\u4e00\u79cd\u81ea\u7136\u7684\u62d3\u6251\u987a\u5e8f\uff0c\u4e0d\u9700\u8981\u989d\u5916\u6392\u5e8f\u6216\u8005\u7528\u961f\u5217\u505a BFS\u3002<\/p>\n
\u5224\u65ad\u00a0it->second > i<\/code>\u00a0\u662f\u4e3a\u4e86\u907f\u514d\u5f80\u56de\u8df3\u6216\u8005\u8df3\u5230\u81ea\u5df1\u8eab\u4e0a\uff0c\u4fdd\u8bc1\u53ea\u5f80\u5750\u6807\u66f4\u5927\u7684\u77f3\u5934\u524d\u8fdb\uff08\u5176\u5b9e\u9898\u76ee\u5750\u6807\u4e25\u683c\u9012\u589e\uff0c\u8df3\u8dc3\u6b65\u957f\u4e3a\u6b63\uff0c\u7406\u8bba\u4e0a nextPos \u4e00\u5b9a\u5927\u4e8e stones[i]\uff0c\u8fd9\u4e2a\u5224\u65ad\u66f4\u591a\u662f\u9632\u5fa1\u6027\u5199\u6cd5\uff0c\u5b9e\u9645\u4e0a indexOf \u91cc\u67e5\u5230\u7684\u4e0b\u6807\u5929\u7136\u5c31\u4f1a\u5927\u4e8e i\uff09\u3002<\/p>\n
\u590d\u6742\u5ea6\u4e0a\uff0c\u6bcf\u5757\u77f3\u5934\u6700\u591a\u53ef\u80fd\u6709 O(n) \u79cd\u4e0d\u540c\u7684\u5230\u8fbe\u6b65\u957f\uff08\u6700\u574f\u60c5\u51b5\u4e0b\u6b65\u957f\u8303\u56f4\u80fd\u5230 n \u8fd9\u4e2a\u91cf\u7ea7\uff09\uff0c\u6240\u4ee5\u603b\u7684\u72b6\u6001\u6570\u662f O(n^2)\uff0c\u6bcf\u4e2a\u72b6\u6001\u5c1d\u8bd5 3 \u79cd\u8df3\u6cd5\uff0c\u6574\u4f53\u65f6\u95f4\u548c\u7a7a\u95f4\u90fd\u662f O(n^2)\uff0c\u5728 LeetCode \u7ed9\u5b9a\u7684\u6570\u636e\u89c4\u6a21\uff08\u77f3\u5934\u6570\u4e0d\u8d85\u8fc7 2000\uff09\u4e0b\u662f\u53ef\u4ee5\u63a5\u53d7\u7684\u3002<\/p>\n
\u4e5f\u53ef\u4ee5\u5199\u6210\u81ea\u9876\u5411\u4e0b\u7684\u8bb0\u5fc6\u5316\u641c\u7d22\u7248\u672c\uff0c\u7528\u00a0unordered_map<long long, int><\/code>\uff08\u628a i \u548c k \u7f16\u7801\u6210\u4e00\u4e2a key\uff09\u505a memo\uff0c\u903b\u8f91\u4e0a\u548c\u4e0a\u9762\u7b49\u4ef7\uff0c\u4f46\u9012\u5f52\u5199\u6cd5\u5728 C++ \u91cc\u6709\u989d\u5916\u7684\u51fd\u6570\u8c03\u7528\u5f00\u9500\uff0c\u4e14\u8981\u6ce8\u610f\u9012\u5f52\u6df1\u5ea6\uff08\u6700\u574f O(n) \u5c42\uff09\uff0c\u4e00\u822c\u63a8\u8350\u7528\u4e0a\u9762\u8fd9\u79cd\u81ea\u5e95\u5411\u4e0a\u8fed\u4ee3\u7684\u5199\u6cd5\uff0c\u66f4\u7a33\u3001\u66f4\u5feb\uff0c\u4e5f\u4e0d\u7528\u62c5\u5fc3\u6808\u6ea2\u51fa\u3002<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
LeetCode 403 \u9752\u86d9\u8df3\u77f3\u5934\uff0c\u672c<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"colormag_page_container_layout":"default_layout","colormag_page_sidebar_layout":"default_layout","footnotes":""},"categories":[24],"tags":[],"class_list":["post-7517","post","type-post","status-publish","format-standard","hentry","category-value_docs"],"_links":{"self":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts\/7517","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/comments?post=7517"}],"version-history":[{"count":0,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts\/7517\/revisions"}],"wp:attachment":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/media?parent=7517"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/categories?post=7517"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/tags?post=7517"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}