Add problem solving (basic)

certificates/README.md

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+# Certificates
+
+To get a certificate, two problems have to be solved within 90 minutes.
+
+The following is an incomplete list of possible problems per certificate as of 2021.09.15:
+
+- [Problem Solving (Basic)](problem-solving-basic)
+    - [Active Traders](problem-solving-basic/active-traders)
+    - [Balanced System Files Partition](problem-solving-basic/balanced-system-files-partition)
+    - [Longest Subarray](problem-solving-basic/longest-subarray)
+    - [Maximum Cost of Laptop Count](problem-solving-basic/maximum-cost-of-laptop-count)
+    - [Nearly Similar Rectangles](problem-solving-basic/nearly-similar-rectangles)
+    - [Parallel Processing](problem-solving-basic/parallel-processing)
+    - [Password Decryption](problem-solving-basic/password-decryption)
+    - [Road Repair](problem-solving-basic/road-repair)
+    - [String Anagram](problem-solving-basic/string-anagram)
+    - [Subarray Sums](problem-solving-basic/subarray-sums)
+    - [Unexpected Demand](problem-solving-basic/unexpected-demand)
+    - [Usernames Changes](problem-solving-basic/usernames-changes)
+    - [Vowel Substring](problem-solving-basic/vowel-substring)
+- [Problem Solving (Intermediate)](problem-solving-intermediate)
+    - [Bitwise AND](problem-solving-intermediate/bitwise-and)
+    - [Equalizing Array Elements](problem-solving-intermediate/equalizing-array-elements)
+    - [File Renaming](problem-solving-intermediate/file-renaming)
+    - [Hotel Construction](problem-solving-intermediate/hotel-construction)
+    - [Largest Area](problem-solving-intermediate/largest-area)
+    - [Maximum Subarray Value](problem-solving-intermediate/maximum-subarray-value)
+    - [Nice Teams](problem-solving-intermediate/nice-teams)
+    - [Sorted Sums](problem-solving-intermediate/sorted-sums)
+    - [Task of Pairing](problem-solving-intermediate/task-of-pairing)
+    - [User-Friendly Password System](problem-solving-intermediate/user-friendly-password-system)
+
+Besides the solutions, there are Python 3 and C++ code stubs and some test cases so you can first try to solve the problems without time pressure if you want to. Keep in mind that most of this is uncommented code that just gets the job done. Nothing more.
+
+# TODO
+- Find more efficient solution for [Maximum Subarray Value](problem-solving-intermediate/maximum-subarray-value). It's getting timeouts for a few test cases.
+- Verify correctness of [Nice Teams](problem-solving-intermediate/nice-teams).

certificates/problem-solving-basic/active-traders/README.md

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+![problem](problem.png)

certificates/problem-solving-basic/active-traders/solution.py

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+#!/bin/python3
+
+import math
+import os
+import random
+import re
+import sys
+
+from collections import defaultdict
+
+#
+# Complete the 'mostActive' function below.
+#
+# The function is expected to return a STRING_ARRAY.
+# The function accepts STRING_ARRAY customers as parameter.
+#
+
+def mostActive(customers):
+    d = defaultdict(int)
+    for c in customers:
+        d[c] += 1
+    return sorted([c for c, cnt in d.items() if cnt / len(customers) >= 0.05])
+
+if __name__ == '__main__':
+    fptr = open(os.environ['OUTPUT_PATH'], 'w')
+
+    customers_count = int(input().strip())
+
+    customers = []
+
+    for _ in range(customers_count):
+        customers_item = input()
+        customers.append(customers_item)
+
+    result = mostActive(customers)
+
+    fptr.write('\n'.join(result))
+    fptr.write('\n')
+
+    fptr.close()

certificates/problem-solving-basic/active-traders/stub.cc

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+#include <bits/stdc++.h>
+
+using namespace std;
+
+string ltrim(const string &);
+string rtrim(const string &);
+
+
+
+/*
+ * Complete the 'mostActive' function below.
+ *
+ * The function is expected to return a STRING_ARRAY.
+ * The function accepts STRING_ARRAY customers as parameter.
+ */
+
+vector<string> mostActive(vector<string> customers) {
+
+}
+
+int main()
+{
+    ofstream fout(getenv("OUTPUT_PATH"));
+
+    string customers_count_temp;
+    getline(cin, customers_count_temp);
+
+    int customers_count = stoi(ltrim(rtrim(customers_count_temp)));
+
+    vector<string> customers(customers_count);
+
+    for (int i = 0; i < customers_count; i++) {
+        string customers_item;
+        getline(cin, customers_item);
+
+        customers[i] = customers_item;
+    }
+
+    vector<string> result = mostActive(customers);
+
+    for (int i = 0; i < result.size(); i++) {
+        fout << result[i];
+
+        if (i != result.size() - 1) {
+            fout << "\n";
+        }
+    }
+
+    fout << "\n";
+
+    fout.close();
+
+    return 0;
+}
+
+string ltrim(const string &str) {
+    string s(str);
+
+    s.erase(
+        s.begin(),
+        find_if(s.begin(), s.end(), not1(ptr_fun<int, int>(isspace)))
+    );
+
+    return s;
+}
+
+string rtrim(const string &str) {
+    string s(str);
+
+    s.erase(
+        find_if(s.rbegin(), s.rend(), not1(ptr_fun<int, int>(isspace))).base(),
+        s.end()
+    );
+
+    return s;
+}

certificates/problem-solving-basic/active-traders/stub.py

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+#!/bin/python3
+
+import math
+import os
+import random
+import re
+import sys
+
+
+
+#
+# Complete the 'mostActive' function below.
+#
+# The function is expected to return a STRING_ARRAY.
+# The function accepts STRING_ARRAY customers as parameter.
+#
+
+def mostActive(customers):
+    # Write your code here
+    pass
+
+if __name__ == '__main__':
+    fptr = open(os.environ['OUTPUT_PATH'], 'w')
+
+    customers_count = int(input().strip())
+
+    customers = []
+
+    for _ in range(customers_count):
+        customers_item = input()
+        customers.append(customers_item)
+
+    result = mostActive(customers)
+
+    fptr.write('\n'.join(result))
+    fptr.write('\n')
+
+    fptr.close()

certificates/problem-solving-basic/active-traders/test-cases/input000.txt

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+20
+Omega
+Alpha
+Omega
+Alpha
+Omega
+Alpha
+Omega
+Alpha
+Omega
+Alpha
+Omega
+Alpha
+Omega
+Alpha
+Omega
+Alpha
+Omega
+Alpha
+Omega
+Beta

certificates/problem-solving-basic/active-traders/test-cases/input001.txt

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+21
+Alpha
+Beta
+Zeta
+Beta
+Zeta
+Zeta
+Epsilon
+Beta
+Zeta
+Beta
+Zeta
+Beta
+Delta
+Zeta
+Beta
+Zeta
+Beta
+Zeta
+Beta
+Zeta
+Beta

certificates/problem-solving-basic/active-traders/test-cases/input002.txt

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+24
+Dog
+Goes
+Woof
+Cat
+Goes
+Meow
+Bird
+Goes
+Tweet
+And
+Mouse
+Goes
+Squeek
+Cow
+Goes
+Moo
+Frog
+Goes
+Croak
+And
+The
+Elephant
+Goes
+Toot

certificates/problem-solving-basic/active-traders/test-cases/input003.txt

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+20
+Bey
+Ddtlcouegmdbyfwu
+Ppuvhifnuap
+Ppuvhifnuap
+Ppuvhifnuap
+Ppuvhifnuap
+Ddtlcouegmdbyfwu
+Ddtlcouegmdbyfwu
+Ppuvhifnuap
+Ppuvhifnuap
+Ppuvhifnuap
+Ppuvhifnuap
+Ddtlcouegmdbyfwu
+Ppuvhifnuap
+Ddtlcouegmdbyfwu
+Ppuvhifnuap
+Ppuvhifnuap
+Ppuvhifnuap
+Ppuvhifnuap
+Ppuvhifnuap

certificates/problem-solving-basic/active-traders/test-cases/input004.txt

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+20
+Bfeo
+Xjgwxtrxi
+Pnnpmud
+Pnnpmud
+Xjgwxtrxi
+Wdswxxrx
+Wdswxxrx
+Xjgwxtrxi
+Wdswxxrx
+Xjgwxtrxi
+Pnnpmud
+Wdswxxrx
+Xjgwxtrxi
+Wdswxxrx
+Xjgwxtrxi
+Xjgwxtrxi
+Wdswxxrx
+Wdswxxrx
+Xjgwxtrxi
+Xjgwxtrxi

certificates/problem-solving-basic/active-traders/test-cases/input005.txt

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+20
+Ampprswkdkobdagw
+Wcfa
+Zooot
+Zn
+Zooot
+Wufeesrvn
+Zn
+Xillkfdvpfpxabqlngd
+Zn
+Zn
+Qvwdrm
+Zn
+Zooot
+Qvwdrm
+Zooot
+Zn
+Zn
+Zooot
+Xillkfdvpfpxabqlngd
+Rskcw

certificates/problem-solving-basic/active-traders/test-cases/input006.txt

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+20
+Exouyfjhnwp
+Van
+Tanwwyoosxtnex
+Omkfnkswrawkjxw
+Zskzazjqtlkiqydpt
+Omkfnkswrawkjxw
+Van
+Sndpvannrywfrnrghlj
+Tanwwyoosxtnex
+Van
+Qpxnlkcwdpdksw
+Qpxnlkcwdpdksw
+Tanwwyoosxtnex
+Zskzazjqtlkiqydpt
+Sndpvannrywfrnrghlj
+Zskzazjqtlkiqydpt
+Tanwwyoosxtnex
+Sndpvannrywfrnrghlj
+Van
+Zskzazjqtlkiqydpt

certificates/problem-solving-basic/active-traders/test-cases/input007.txt

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+20
+Ami
+Wuxavlwftgyxxhpygs
+Wk
+Vwfnbngh
+Wmzheqx
+Wuxavlwftgyxxhpygs
+Oxhaiafmvkb
+Wk
+Wuxavlwftgyxxhpygs
+Wmzheqx
+Vwfnbngh
+Vwfnbngh
+Wmzheqx
+Ocni
+Xjmornquma
+Wmzheqx
+Xjmornquma
+Ltpwmhqw
+Wk
+Ocni