It is already well-known that using unordered series in Codeforces is super dangerous, and it is not recommended to use them at all unless you know how to prevent them properly (well, even if you know, just using a regular map or set is more beneficial in most cases). Thanks to ...
For the first time I have seen unordered map with this custom hash is getting TLE because of it. (Custom hash fromblog) structcustom_hash{staticuint64_tsplitmix64(uint64_tx){x+=0x9e3779b97f4a7c15;x=(x^(x>>30))*0xbf58476d1ce4e5b9;x=(x^(x>>27))*0x94d049bb133111eb;returnx...
目录 收起 例题 结论 补充:unordered_map复杂度退化的具体原因 例题 起因是一道水题:Problem - C - Codeforces Problem - C - Codeforcescodeforces.com/contest/1598/problem/C 题意大致为从一个数量级为2e5 的数组中查找和等于特定值的下标对数,有点类似于Leetcode第一题。 例如在 [1, 2, 3, ...
在c++11 里面,unordered_set和unordered_map就可以做到单次操作O(1)O(1)(基于哈希)。 但在Codeforces 的比赛上面,尽量别用unoredered_set / unoredered_map。 一是因为unordered_map本身自带大常数,有时候跑的甚至没有map快。 第二个原因也是最重要的原因是,很多 CF 上的大神直接根据 STL 的源代码来造出 h...
防止unordered_map 被卡方法 codeforces 上看到的,mark 一下代码。原作者:neal,原链接:https://codeforces.com/blog/entry/62393struct custom_hash { static uint64_t splitmix64(uint64_t x) { // http://xorshift.di.unimi.it/splitmix64.c x += ...
就可以避免针对默认参数的hack,同时unordered_map的速度可以提升约10倍。 当然平时还是别偷懒加上快读快写,希望人别被卡 ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); 更多的关于unordered_map的细节可以学习cf大佬blog的评论区 https://codeforces.com/blog/entry/21853codefo...
只要我把unordered_map/unordered_set换成map/set就可以编译通过。请问为什么呢? 全部评论 推荐 最新 楼层hurley 同济大学 C++ #include <bits/stdc++.h> using namespace std;点赞 回复 分享 发布于 2021-04-07 22:15 竹201812122137757 佳木斯大学 C++ 额 要怎么添加头文件啊 点赞 回复 分享 发布于 ...
codeforces 1096D Easy Problem dp D. Easy Problem time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Vasya is preparing a contest, and now he has written a statement for an ea......
unordered_map of n elements is not actually O(n^2), but O(n) amortized. The reason O(n^2) is theoretically possible is due to something called a hash collision, which is where a hash function generates the same value for 2 elements inserted into a map. When this happens, a rehash ...
voidsolve(){intn,k;cin>>n>>k;vi g;unordered_map<int,int>m;for(inti=0;i<n;i++){inta;cin>>a;m[a]++;}for(auto&x:m){if(x.second>=k){g.pb(x.first);}}if(g.size()==0){cout<<-1<<"\n";return;}Asort(g);intl=0,r=-1,cl=g[0];n=g.size();for(inti=1;i<n;...