STL Data Structures: set and map - Introduction to Programming - C++

STL Data Structures: set and map - Introduction to Programming - C++

#include <bits/stdc++.h>
using namespace std;

int main() {
    set<int> s;          // empty set of ints
    s.insert(5);
    s.insert(1);
    s.insert(3);
    s.insert(3);         // duplicate, ignored

    // s now contains {1, 3, 5}

    if (s.find(3) != s.end()) {
        cout << "3 is in the set\n";
    }

    s.erase(1);          // remove key 1 if present

    for (int x : s) {
        cout << x << " "; // prints: 3 5
    }
    cout << "\n";
}

#include <bits/stdc++.h>
using namespace std;

int main() {
    map<string, int> freq;

    freq["apple"]++;
    freq["banana"] += 2;
    freq["orange"] = 5;

    // Iteration goes in lexicographical order of keys
    for (auto &[word, count] : freq) {
        cout << word << " -> " << count << "\n";
    }

    if (freq.count("apple")) {
        cout << "apple appears " << freq["apple"] << " times\n";
    }

    return 0;
}

#include <bits/stdc++.h>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n;
    cin >> n;
    set<int> s;

    for (int i = 0; i < n; i++) {
        int x;
        cin >> x;
        s.insert(x);
    }

    cout << s.size() << "\n";
    return 0;
}

#include <bits/stdc++.h>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, q;
    cin >> n >> q;
    set<int> s;
    for (int i = 0; i < n; i++) {
        int x;
        cin >> x;
        s.insert(x);
    }

    while (q--) {
        int x;
        cin >> x;
        auto it = s.lower_bound(x);
        if (it == s.end()) {
            cout << "NO\n";
        } else {
            cout << *it << "\n";
        }
    }
    return 0;
}

#include <bits/stdc++.h>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n;
    cin >> n;
    map<string, int> freq;
    for (int i = 0; i < n; i++) {
        string w;
        cin >> w;
        freq[w]++; // creates key if not present
    }

    for (auto &[word, count] : freq) {
        cout << word << " " << count << "\n";
    }

    return 0;
}

#include <bits/stdc++.h>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n;
    cin >> n;
    vector<int> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }

    set<int> s(a.begin(), a.end()); // distinct sorted values

    map<int, int> comp; // value -> compressed index
    int id = 0;
    for (int x : s) {
        comp[x] = id++;
    }

    for (int i = 0; i < n; i++) {
        a[i] = comp[a[i]];
    }

    for (int i = 0; i < n; i++) {
        cout << a[i] << " ";
    }
    cout << "\n";

    return 0;
}