Advice C++ InfoClock

main.cpp

// Includes all headers
#include <bits/stdc++.h>

// Don't be afraid to use constants
const int N = 1024;

void do_not_use_endl() {
    vector<int> primes {2, 3, 5, 8, 11};
    
    // Let's tail -f the output file
    for (int i=0; i<primes.size(); i++) { // Use variables as local as possible
        cout << primes[i] << endl; // This flushes the output everytime
        sleep(1);
    }

    cout << "Now with newline\n";

    for (int x : primes) { // Nice syntax for iterating
        cout << x << "\n";
        sleep(1);
    }
}

void sexy_pairs() {
    cout << "=== Pairs\n";
    string day = "Monday";
    // equivalent to
    string same_day {"Monday"};
    pair<int, string> my_pair {1, day};
    cout << my_pair.first << " " << my_pair.second << "\n";
    
    // Containers
    vector<pair<int, string>> weekdays;
    weekdays.push_back(my_pair);
    weekdays.push_back({2, "Tuesday"});

    cout << "=== Range loops";
    for (auto p : weekdays) {
        cout << p.first << " - " << p.second << "\n";
    }
}

void lambdas() {
    vector<pair<int, int>> v;
    for (int i=0; i<10; i++) {
        v.push_back({rand() % 10, rand() % 20});
    }
    
    sort(v.begin(), v.end(), [] (pair<int,int> a, pair<int,int> b) {
        return a.second > b.second;
    });
    
    for (auto p : v) {
        cout << p.first << " - " << p.second << "\n";
    }
}

void hashes() {
    // O(1) access/update time... but it's unordered
    unordered_map<string, int> hash;

    hash["python"] = 42;
    hash["infoclock"] = 333;
    hash["wine"] = 70;

    for (auto p : hash) {
        cout << p.first << " - " << p.second << "\n";
    }
}

int main() {
    // This isn't executed on Codeforces/Infoarena.
    #ifndef ONLINE_JUDGE
    freopen("cdf.out", "w", stdout);
    #endif

    // Read this before http://algopedia.ro/wiki/index.php/Note_de_curs,_clasele_11-12,_21_noiembrie_2013
    
    srand(time(NULL));

    // Constructor for an array of 100 zeros.
    vector<int> v(N, 0);
    
    do_not_use_endl();
    sexy_pairs();
    lambdas();
    hashes();
    
    return 0;
}