{"id":3403,"date":"2026-07-09T10:58:20","date_gmt":"2026-07-09T10:58:20","guid":{"rendered":"https:\/\/csofferprep.com\/citadel-swe-oa-hackerrank-bfs-timed-coding\/"},"modified":"2026-07-10T00:00:06","modified_gmt":"2026-07-10T00:00:06","slug":"citadel-swe-oa-hackerrank-bfs-timed-coding","status":"publish","type":"post","link":"https:\/\/csofferprep.com\/en\/oa\/citadel-swe-oa-hackerrank-bfs-timed-coding\/","title":{"rendered":"Citadel SWE OA \u9762\u7ecf\uff5cHackerRank \u7b97\u6cd5\u9898\u3001BFS \u4e0e\u9ad8\u538b\u9650\u65f6\u9898\u578b\u89e3\u6790"},"content":{"rendered":"
\"Citadel<\/figure>\n

Citadel SWE OA \u7684\u8282\u594f\u5f88\u76f4\u63a5\uff1a\u9650\u65f6\u3001\u5f3a\u6d4b\u8bd5\u3001\u9898\u76ee\u4e0d\u7ed5\u5f2f\uff0c\u4f46\u4f18\u5316\u548c\u8fb9\u754c\u8981\u6c42\u5f88\u9ad8\u3002\u51c6\u5907\u65f6\u4e0d\u8981\u53ea\u5237\u80fd AC \u7684\u6a21\u677f\uff0c\u8981\u7ec3\u5230\u80fd\u5728 75 \u5206\u949f\u5de6\u53f3\u5199\u5b8c\u4e24\u5230\u4e09\u9053 medium-hard \u9898\uff0c\u5e76\u628a\u590d\u6742\u5ea6\u89e3\u91ca\u6e05\u695a\u3002\u53ef\u4ee5\u5148\u770b Citadel Software Engineer interview guide<\/a>\uff0c\u518d\u6309 HackerRank \u73af\u5883\u7ec3\u8ba1\u65f6\u63d0\u4ea4\u3002<\/p>\n

\u7b2c\u4e00\u9898\uff1aSubarray Remainder Counter<\/h2>\n

Question description<\/h3>\n

Given an array of integers Nums<\/code> \u548c\u6b63\u6574\u6570 k<\/code>\uff0c\u8981\u6c42\u7edf\u8ba1\u6709\u591a\u5c11\u4e2a\u8fde\u7eed\u5b50\u6570\u7ec4\u7684\u548c\u53ef\u4ee5\u88ab k<\/code> \u6574\u9664\u3002\u6570\u7ec4\u91cc\u6709\u8d1f\u6570\uff0c\u957f\u5ea6\u53ef\u4ee5\u5230 2 * 10^5<\/code>\uff0c\u7ed3\u679c\u7528 64 \u4f4d\u6574\u6570\u8fd4\u56de\u3002<\/p>\n

Problem-solving ideas<\/h3>\n

\u524d\u7f00\u548c\u53d6\u6a21\u540e\uff0c\u5982\u679c\u4e24\u4e2a\u4f4d\u7f6e\u7684\u4f59\u6570\u76f8\u540c\uff0c\u4e2d\u95f4\u8fd9\u6bb5\u5b50\u6570\u7ec4\u7684\u548c\u5c31\u80fd\u88ab k<\/code> \u6574\u9664\u3002\u626b\u63cf\u6570\u7ec4\u65f6\u7ef4\u62a4 remainder -> count<\/code>\uff0c\u521d\u59cb\u653e\u5165\u4f59\u6570 0 \u4e00\u6b21\u3002\u6bcf\u8bfb\u4e00\u4e2a\u6570\uff0c\u66f4\u65b0\u5f53\u524d\u524d\u7f00\u4f59\u6570\uff0c\u5148\u628a\u5df2\u6709\u540c\u4f59\u6570\u91cf\u52a0\u5230\u7b54\u6848\u91cc\uff0c\u518d\u628a\u5f53\u524d\u4f59\u6570\u8ba1\u6570\u52a0\u4e00\u3002\u8d1f\u6570\u8981\u7528 (x % k + k) % k<\/code> \u89c4\u6574\uff0c\u5426\u5219\u4e0d\u540c\u8bed\u8a00\u91cc\u8d1f\u4f59\u6570\u4f1a\u8ba9\u9690\u85cf\u6d4b\u8bd5\u6302\u6389\u3002\u8fd9\u4e2a\u9898\u7684\u6838\u5fc3\u662f\u54c8\u5e0c\u8868\u8ba1\u6570\uff0c\u771f\u6b63\u5361\u4eba\u7684\u662f 64 \u4f4d\u7ed3\u679c\u3001\u8d1f\u6570\u53d6\u6a21\u548c\u521d\u59cb\u7a7a\u524d\u7f00\u3002Complexity<\/strong>\uff1a\u65f6\u95f4 O(n)\uff0c\u7a7a\u95f4 O(k) \u6216 O(n)\u3002<\/p>\n

\u7b2c\u4e8c\u9898\uff1aBFS Maze With Keys<\/h2>\n

Question description<\/h3>\n

\u7ed9\u5b9a\u4e00\u4e2a\u4e8c\u7ef4\u8ff7\u5bab\uff0cS<\/code> \u662f\u8d77\u70b9\uff0cT<\/code> \u662f\u7ec8\u70b9\uff0c#<\/code> It's a wall,a-f<\/code> \u662f\u94a5\u5319\uff0cA-F<\/code> \u662f\u95e8\u3002\u6bcf\u8d70\u4e00\u6b65\u6210\u672c\u4e3a 1\uff0c\u53ea\u6709\u62ff\u5230\u5bf9\u5e94\u5c0f\u5199\u94a5\u5319\u540e\u624d\u80fd\u7a7f\u8fc7\u5927\u5199\u95e8\u3002\u8fd4\u56de\u4ece S<\/code> Arrive T<\/code> \u7684\u6700\u77ed\u6b65\u6570\uff0c\u65e0\u6cd5\u5230\u8fbe\u8fd4\u56de -1<\/code>.<\/p>\n

Problem-solving ideas<\/h3>\n

\u72b6\u6001\u4e0d\u80fd\u53ea\u7528\u5750\u6807\uff0c\u5fc5\u987b\u628a\u94a5\u5319\u96c6\u5408\u653e\u8fdb\u72b6\u6001\u91cc\u3002\u7528 bitmask \u8868\u793a\u5df2\u7ecf\u62ff\u5230\u7684\u94a5\u5319\uff0cBFS \u961f\u5217\u5143\u7d20\u662f (r, c, mask, dist)<\/code>\uff0cvisited \u7528\u4e09\u7ef4\u7ed3\u6784\u6216\u54c8\u5e0c\u96c6\u5408\u8bb0\u5f55 (r, c, mask)<\/code>\u3002\u9047\u5230\u94a5\u5319\u5c31\u628a\u5bf9\u5e94 bit \u7f6e 1\uff1b\u9047\u5230\u95e8\u5148\u68c0\u67e5 bit\uff0c\u4e0d\u6ee1\u8db3\u5c31\u8df3\u8fc7\u3002\u56e0\u4e3a\u6bcf\u6761\u8fb9\u6210\u672c\u76f8\u540c\uff0c\u7b2c\u4e00\u6b21\u5230\u8fbe T<\/code> \u5c31\u662f\u6700\u77ed\u8def\u5f84\u3002\u7f51\u683c\u5927\u65f6\u8981\u907f\u514d\u628a path \u5b57\u7b26\u4e32\u653e\u8fdb\u961f\u5217\uff0c\u53ea\u5b58\u72b6\u6001\u548c\u8ddd\u79bb\u3002\u7c7b\u4f3c\u7684\u6700\u77ed\u8def\u72b6\u6001\u538b\u7f29\u9898\u53ef\u4ee5\u53c2\u8003 Shortest Path in Binary Matrix<\/a> \u7684 BFS \u5199\u6cd5\uff0c\u518d\u628a\u94a5\u5319\u7ef4\u5ea6\u52a0\u8fdb\u53bb\u3002Complexity<\/strong>\uff1a\u65f6\u95f4 O(mn * 2^K)\uff0c\u7a7a\u95f4 O(mn * 2^K)\uff0cK \u662f\u94a5\u5319\u6570\u91cf\u3002<\/p>\n

\u7b2c\u4e09\u9898\uff1aStreaming Median<\/h2>\n

Question description<\/h3>\n

\u7cfb\u7edf\u6301\u7eed\u6536\u5230\u4ea4\u6613\u5ef6\u8fdf\u6570\u636e latency_ms<\/code>\uff0c\u9700\u8981\u652f\u6301\u4e24\u4e2a\u64cd\u4f5c\uff1aadd(value)<\/code> \u52a0\u5165\u4e00\u4e2a\u5ef6\u8fdf\u503c\uff0cmedian()<\/code> \u8fd4\u56de\u5f53\u524d\u6240\u6709\u5ef6\u8fdf\u7684\u4e2d\u4f4d\u6570\u3002\u6570\u636e\u91cf\u5f88\u5927\uff0c\u4e0d\u80fd\u6bcf\u6b21\u67e5\u8be2\u90fd\u91cd\u65b0\u6392\u5e8f\u3002<\/p>\n

Problem-solving ideas<\/h3>\n

\u7528\u4e24\u4e2a\u5806\u7ef4\u62a4\u4e2d\u4f4d\u6570\u3002\u5de6\u8fb9\u662f\u5927\u9876\u5806\uff0c\u4fdd\u5b58\u8f83\u5c0f\u7684\u4e00\u534a\uff1b\u53f3\u8fb9\u662f\u5c0f\u9876\u5806\uff0c\u4fdd\u5b58\u8f83\u5927\u7684\u4e00\u534a\u3002\u63d2\u5165\u65f6\u5148\u6839\u636e\u5f53\u524d\u5806\u9876\u51b3\u5b9a\u653e\u54ea\u8fb9\uff0c\u518d\u505a rebalance\uff0c\u8ba9\u4e24\u4e2a\u5806\u5927\u5c0f\u5dee\u4e0d\u8d85\u8fc7 1\u3002\u67e5\u8be2\u65f6\uff0c\u5982\u679c\u603b\u6570\u4e3a\u5947\u6570\uff0c\u8fd4\u56de\u5143\u7d20\u66f4\u591a\u90a3\u8fb9\u7684\u5806\u9876\uff1b\u5982\u679c\u4e3a\u5076\u6570\uff0c\u8fd4\u56de\u4e24\u4e2a\u5806\u9876\u5e73\u5747\u503c\u3002\u5b9e\u73b0\u7ec6\u8282\u8981\u5904\u7406\u7a7a\u5806\u3001\u5076\u6570\u5e73\u5747\u6ea2\u51fa\u3001\u91cd\u590d\u503c\u548c\u8d1f\u6570\u3002\u8fd9\u4e2a\u9898\u5728\u4ea4\u6613\u7cfb\u7edf\u8bed\u5883\u91cc\u4f1a\u8ffd\u95ee\u6ed1\u52a8\u7a97\u53e3\u4e2d\u4f4d\u6570\uff0cfollow-up \u53ef\u4ee5\u518d\u5f15\u5165\u5ef6\u8fdf\u5220\u9664\u54c8\u5e0c\u8868\u3002Complexity<\/strong>\uff1a\u63d2\u5165 O(log n)\uff0c\u67e5\u8be2 O(1)\uff0c\u7a7a\u95f4 O(n)\u3002<\/p>\n

Exam preparation advice<\/h2>\n

Citadel OA \u8981\u628a prefix sum\u3001BFS\/DFS\u3001\u5806\u3001DP\u3001\u56fe\u6700\u77ed\u8def\u548c\u72b6\u6001\u538b\u7f29\u5237\u5230\u9650\u65f6\u53ef\u5199\u3002\u505a\u9898\u65f6\u5148\u5199\u51fa\u80fd\u89e3\u91ca\u7684\u6b63\u786e\u89e3\uff0c\u518d\u5904\u7406\u5927\u6570\u636e\u8fb9\u754c\u3002HackerRank \u8f93\u5165\u8f93\u51fa\u4e5f\u8981\u63d0\u524d\u7ec3\uff0c\u5c24\u5176\u662f\u591a case\u300164 \u4f4d\u7ed3\u679c\u548c\u81ea\u5b9a\u4e49 parser\u3002Glassdoor \u4e0a\u7684 Citadel SWE \u9762\u8bd5\u8bb0\u5f55\u91cc\u4e5f\u63d0\u5230 BFS\u3001stack \u548c\u591a\u9898\u9650\u65f6\uff0c\u8fd9\u7c7b\u9898\u4e0d\u9002\u5408\u4e34\u573a\u624d\u56de\u5fc6\u6a21\u677f\u3002<\/p>\n

FAQ<\/h2>\n

Citadel SWE OA \u8981\u6309\u4ec0\u4e48\u96be\u5ea6\u51c6\u5907\uff1f<\/h3>\n

\u6309 LeetCode Medium \u5230 Hard \u51c6\u5907\u3002\u7b80\u5355\u9898\u53ef\u4ee5\u70ed\u8eab\uff0c\u4f46\u4e3b\u8bad\u7ec3\u8981\u653e\u5728\u9700\u8981\u4f18\u5316\u3001\u8bc1\u660e\u548c\u8fb9\u754c\u5904\u7406\u7684\u9898\u4e0a\u3002<\/p>\n

HackerRank \u73af\u5883\u6700\u5bb9\u6613\u51fa\u4ec0\u4e48\u95ee\u9898\uff1f<\/h3>\n

\u8f93\u5165\u89e3\u6790\u3001long long\u3001\u8d1f\u6570\u53d6\u6a21\u3001\u6570\u7ec4\u8d8a\u754c\u548c\u6ca1\u6709\u8986\u76d6\u7a7a\u8f93\u5165\u3002\u63d0\u4ea4\u524d\u7528\u6781\u5c0f\u6837\u4f8b\u3001\u91cd\u590d\u503c\u3001\u5927\u6570\u548c\u6781\u7aef\u7a97\u53e3\u5404\u8dd1\u4e00\u904d\u3002<\/p>\n

BFS \u9898\u600e\u4e48\u907f\u514d\u5199\u4e71\uff1f<\/h3>\n

\u5148\u5b9a\u4e49\u72b6\u6001\uff0c\u518d\u5b9a\u4e49\u8f6c\u79fb\u3002\u53ea\u8981\u72b6\u6001\u91cc\u5c11\u4e86\u94a5\u5319\u3001\u5269\u4f59\u6b65\u6570\u3001\u65b9\u5411\u6216\u8d44\u6e90\u8fd9\u79cd\u7ef4\u5ea6\uff0cvisited \u5c31\u4f1a\u63d0\u524d\u526a\u6389\u6b63\u786e\u8def\u5f84\u3002<\/p>\n

\u5173\u4e8e CSOFFERPREP<\/h2>\n

\u8fdb VO \u4e4b\u524d\uff0c\u53ef\u4ee5\u627e CSOFFERPREP \u505a\u5b9e\u65f6\u9762\u8bd5\u52a9\u653b\u548c\u5907\u8003\u8f85\u5bfc\u3002CSOFFERPREP \u6df1\u8015\u5317\u7f8e IT \u884c\u4e1a\u591a\u5e74\uff0c\u5df2\u5e2e\u52a9\u4e07\u4f59\u540d\u5b66\u751f\u8fdb\u5165\u5168\u7403 500 \u5f3a\u4f01\u4e1a\u3002\u5bfc\u5e08\u6765\u81ea\u4e00\u7ebf\u5927\u5382\u8d44\u6df1\u5de5\u7a0b\u5e08\u548c\u9762\u8bd5\u5b98\uff0c\u5bf9 Citadel \u8fd9\u7c7b\u6ce8\u91cd\u7b97\u6cd5\u548c\u5de5\u7a0b\u8868\u8fbe\u7684\u516c\u53f8\u7684\u9762\u8bd5\u5957\u8def\u5f88\u719f\u6089\u3002\u65e0\u8bba\u662f OA\u8f85\u52a9\u3001OA \u8f85\u5bfc\u3001VO \u8f85\u52a9\u3001VO \u6a21\u62df\u9762\u8bd5\u3001VO \u8f85\u52a9\u8fd8\u662f\u7cfb\u7edf\u8bbe\u8ba1\u8f85\u52a9\uff0c\u90fd\u53ef\u4ee5\u83b7\u5f97\u66f4\u6709\u9488\u5bf9\u6027\u7684\u51c6\u5907\u65b9\u6848\uff1aCSOFFERPREP \u00b7 \u670d\u52a1\u8be6\u60c5<\/a><\/p>\n

\u53c2\u8003\u6765\u6e90<\/h2>\n