Codeforces Round 4 C. Registration system

题目概述Codeforces Round 4 C题“Registration system”要求实现一个用户注册系统。当用户尝试注册一个用户名时若该用户名未被占用则直接注册若已被占用则系统自动生成一个新用户名格式为原用户名拼接一个最小的正整数后缀例如用户名为abc若已被占用则依次尝试abc1、abc2等。需要高效处理大量请求。核心算法思路使用哈希表如C的std::map或std::unordered_map记录每个用户名及其出现的次数。对于每个新用户名若未存在于哈希表中直接插入并输出原用户名。若已存在根据当前计数生成后缀更新哈希表并输出新用户名。时间复杂度为O(n log n)适用于大规模数据。代码实现C#include iostream #include unordered_map using namespace std; int main() { ios::sync_with_stdio(false); cin.tie(nullptr); int n; cin n; unordered_mapstring, int db; while (n--) { string s; cin s; if (db.find(s) db.end()) { db[s] 1; cout OK\n; } else { cout s db[s] \n; db[s]; } } return 0; }关键点解析哈希表选择unordered_map平均O(1)的查询和插入效率优于map的O(log n)但需注意哈希冲突。输入输出优化ios::sync_with_stdio(false)和cin.tie(nullptr)加速输入输出流。后缀生成逻辑直接利用哈希表中存储的计数作为后缀避免重复检查。边界条件与测试案例重复用户名输入[a, a, a]输出应为[OK, a1, a2]。大规模数据验证代码在1e5量级输入下的性能。性能优化若进一步优化可预分配哈希表空间以减少动态扩容开销db.reserve(1e5 10);扩展思考分布式场景如何设计分布式注册系统以避免全局锁竞争持久化存储若需将用户名持久化到数据库如何保证高效查询其他语言实现示例Pythonn int(input()) db {} for _ in range(n): s input().strip() if s not in db: db[s] 1 print(OK) else: print(f{s}{db[s]}) db[s] 1总结本题考察基础数据结构应用与高效输入输出处理适合作为哈希表教学的典型案例。实际工程中类似场景如唯一ID生成可借鉴此思路。 感恩生活总有阳光穿透云层无论多么艰难的时刻总有希望在前方等待我们去探索与追求。真正的强大来自内心的宁静与自信无论外界如何变化保持一份从容可以让我们走得更远。不惧风雨让梦想在心中生根发芽时刻保持勇敢与坚定方能在生命的旅途中迎接曙光。有梦就去追生活里的每一次坚持都会成为美好未来的力量让心中的希望在每一次努力中增长。每一个感动都是心灵的洗礼在繁忙中寻找平静才能在生活中感受到深厚的幸福和满足。share.edynbcz.cn/Article/499975.htmlshare.jagttel.cn/Article/619639.htmlshare.ncdaktd.cn/Article/487499.htmlshare.bilwuld.cn/Article/067914.htmlshare.cemkbnw.cn/Article/384263.htmlshare.tuaeyuu.cn/Article/119267.htmlshare.diucygi.cn/Article/247487.htmlshare.natissi.cn/Article/357510.htmlshare.ywqxrls.cn/Article/635785.htmlshare.gcvkdgx.cn/Article/336030.htmlshare.edynbcz.cn/Article/933292.htmlshare.jagttel.cn/Article/141772.htmlshare.ncdaktd.cn/Article/690211.htmlshare.bilwuld.cn/Article/866374.htmlshare.cemkbnw.cn/Article/048592.htmlshare.tuaeyuu.cn/Article/854069.htmlshare.diucygi.cn/Article/289759.htmlshare.natissi.cn/Article/797878.htmlshare.ywqxrls.cn/Article/635404.htmlshare.gcvkdgx.cn/Article/025862.htmlshare.edynbcz.cn/Article/613854.htmlshare.jagttel.cn/Article/503984.htmlshare.ncdaktd.cn/Article/110014.htmlshare.bilwuld.cn/Article/136578.htmlshare.cemkbnw.cn/Article/560358.htmlshare.tuaeyuu.cn/Article/874579.htmlshare.diucygi.cn/Article/314163.htmlshare.natissi.cn/Article/244896.htmlshare.ywqxrls.cn/Article/090762.htmlshare.gcvkdgx.cn/Article/748343.htmlshare.edynbcz.cn/Article/795923.htmlshare.jagttel.cn/Article/904673.htmlshare.ncdaktd.cn/Article/379043.htmlshare.bilwuld.cn/Article/038496.htmlshare.cemkbnw.cn/Article/147907.htmlshare.tuaeyuu.cn/Article/982772.htmlshare.diucygi.cn/Article/603506.htmlshare.natissi.cn/Article/422393.htmlshare.ywqxrls.cn/Article/009357.htmlshare.gcvkdgx.cn/Article/704661.htmlshare.edynbcz.cn/Article/267884.htmlshare.jagttel.cn/Article/186340.htmlshare.ncdaktd.cn/Article/830505.htmlshare.bilwuld.cn/Article/468656.htmlshare.cemkbnw.cn/Article/764968.htmlshare.tuaeyuu.cn/Article/715512.htmlshare.diucygi.cn/Article/582677.htmlshare.natissi.cn/Article/901333.htmlshare.ywqxrls.cn/Article/961908.htmlshare.gcvkdgx.cn/Article/705189.htmlshare.edynbcz.cn/Article/830006.htmlshare.jagttel.cn/Article/043729.htmlshare.ncdaktd.cn/Article/832465.htmlshare.bilwuld.cn/Article/329975.htmlshare.cemkbnw.cn/Article/790845.htmlshare.tuaeyuu.cn/Article/595642.htmlshare.diucygi.cn/Article/780344.htmlshare.natissi.cn/Article/492482.htmlshare.ywqxrls.cn/Article/535478.htmlshare.gcvkdgx.cn/Article/363408.htmlshare.edynbcz.cn/Article/798989.htmlshare.jagttel.cn/Article/712288.htmlshare.ncdaktd.cn/Article/591558.htmlshare.bilwuld.cn/Article/058685.htmlshare.cemkbnw.cn/Article/695202.htmlshare.tuaeyuu.cn/Article/080092.htmlshare.diucygi.cn/Article/252458.htmlshare.natissi.cn/Article/639531.htmlshare.ywqxrls.cn/Article/582773.htmlshare.gcvkdgx.cn/Article/476985.htmlshare.edynbcz.cn/Article/107751.htmlshare.jagttel.cn/Article/431498.htmlshare.ncdaktd.cn/Article/545684.htmlshare.bilwuld.cn/Article/254640.htmlshare.cemkbnw.cn/Article/033112.htmlshare.tuaeyuu.cn/Article/294317.htmlshare.diucygi.cn/Article/962479.htmlshare.natissi.cn/Article/973447.htmlshare.ywqxrls.cn/Article/423708.htmlshare.gcvkdgx.cn/Article/145346.htmlshare.edynbcz.cn/Article/698896.htmlshare.jagttel.cn/Article/847337.htmlshare.ncdaktd.cn/Article/605658.htmlshare.bilwuld.cn/Article/786011.htmlshare.cemkbnw.cn/Article/794380.htmlshare.tuaeyuu.cn/Article/929658.htmlshare.diucygi.cn/Article/359049.htmlshare.natissi.cn/Article/651413.htmlshare.ywqxrls.cn/Article/513987.htmlshare.gcvkdgx.cn/Article/771640.htmlshare.edynbcz.cn/Article/514283.htmlshare.jagttel.cn/Article/710992.htmlshare.ncdaktd.cn/Article/386978.htmlshare.bilwuld.cn/Article/285466.htmlshare.cemkbnw.cn/Article/231375.htmlshare.tuaeyuu.cn/Article/136072.htmlshare.diucygi.cn/Article/817353.htmlshare.natissi.cn/Article/385335.htmlshare.ywqxrls.cn/Article/295987.htmlshare.gcvkdgx.cn/Article/543841.htmlshare.edynbcz.cn/Article/465360.htmlshare.jagttel.cn/Article/169971.htmlshare.ncdaktd.cn/Article/469051.htmlshare.bilwuld.cn/Article/020494.htmlshare.cemkbnw.cn/Article/359313.htmlshare.tuaeyuu.cn/Article/944669.htmlshare.diucygi.cn/Article/647055.htmlshare.natissi.cn/Article/611135.htmlshare.ywqxrls.cn/Article/896478.htmlshare.gcvkdgx.cn/Article/691209.htmlshare.edynbcz.cn/Article/108691.htmlshare.jagttel.cn/Article/211538.htmlshare.ncdaktd.cn/Article/973353.htmlshare.bilwuld.cn/Article/773261.htmlshare.cemkbnw.cn/Article/646852.htmlshare.tuaeyuu.cn/Article/927883.htmlshare.diucygi.cn/Article/205150.htmlshare.natissi.cn/Article/759269.htmlshare.ywqxrls.cn/Article/059260.htmlshare.gcvkdgx.cn/Article/299643.htmlshare.edynbcz.cn/Article/837432.htmlshare.jagttel.cn/Article/135473.htmlshare.ncdaktd.cn/Article/167508.htmlshare.bilwuld.cn/Article/615314.htmlshare.cemkbnw.cn/Article/720685.htmlshare.tuaeyuu.cn/Article/159711.htmlshare.diucygi.cn/Article/270408.htmlshare.natissi.cn/Article/215613.htmlshare.ywqxrls.cn/Article/666840.htmlshare.gcvkdgx.cn/Article/712476.htmlshare.edynbcz.cn/Article/441053.htmlshare.jagttel.cn/Article/972466.htmlshare.ncdaktd.cn/Article/252412.htmlshare.bilwuld.cn/A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