Iterators, Algorithms & Lambdas

#include <iostream>
#include <vector>
#include <list>
using namespace std;

int main() {
    vector<int> v = {10, 20, 30, 40};
    for (vector<int>::iterator it = v.begin(); it != v.end(); ++it)
        cout << *it << " ";                    // dereference like a pointer
    cout << endl;

    list<string> names = {"Asha", "Ravi", "Meera"};
    for (auto it = names.rbegin(); it != names.rend(); ++it)   // reverse iterators
        cout << *it << " ";
    cout << endl;
    return 0;
}

10 20 30 40 
Meera Ravi Asha

#include <iostream>
using namespace std;

int main() {
    auto square = [](int x) { return x * x; };
    int bonus = 5;
    auto addBonus = [bonus](int m) { return m + bonus; };     // captures bonus by value
    int calls = 0;
    auto counter = [&calls]() { calls++; };                    // captures calls by reference
    counter(); counter(); counter();
    cout << square(7) << " " << addBonus(80) << " " << calls << endl;
    return 0;
}

49 85 3

#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <string>
using namespace std;

void show(const vector<int> &v) { for (int x : v) cout << x << " "; cout << endl; }

int main() {
    vector<int> v = {42, 7, 19, 7, 88, 3, 25};

    sort(v.begin(), v.end());                                   // ascending
    cout << "sorted:        "; show(v);
    sort(v.begin(), v.end(), [](int a, int b) { return a > b; });   // descending
    cout << "descending:    "; show(v);

    cout << "max element:   " << *max_element(v.begin(), v.end()) << endl;
    cout << "sum:           " << accumulate(v.begin(), v.end(), 0) << endl;
    cout << "count of 7:    " << count(v.begin(), v.end(), 7) << endl;
    cout << "count > 20:    " << count_if(v.begin(), v.end(), [](int x) { return x > 20; }) << endl;

    auto it = find(v.begin(), v.end(), 19);
    cout << "19 found at index " << (it - v.begin()) << endl;

    sort(v.begin(), v.end());
    cout << "binary_search 25: " << boolalpha << binary_search(v.begin(), v.end(), 25) << endl;
    v.erase(unique(v.begin(), v.end()), v.end());              // remove adjacent duplicates
    cout << "unique:        "; show(v);
    reverse(v.begin(), v.end());
    cout << "reversed:      "; show(v);

    vector<int> doubled(v.size());
    transform(v.begin(), v.end(), doubled.begin(), [](int x) { return 2 * x; });
    cout << "doubled:       "; show(doubled);
    return 0;
}

sorted:        3 7 7 19 25 42 88 
descending:    88 42 25 19 7 7 3 
max element:   88
sum:           191
count of 7:    2
count > 20:    3
19 found at index 3
binary_search 25: true
unique:        3 7 19 25 42 88 
reversed:      88 42 25 19 7 3 
doubled:       176 84 50 38 14 6

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
using namespace std;

struct Student { string name; int marks; };

int main() {
    vector<Student> cls = {{"Asha", 88}, {"Ravi", 95}, {"Meera", 88}, {"Kiran", 72}};
    stable_sort(cls.begin(), cls.end(), [](const Student &a, const Student &b) {
        return a.marks > b.marks;               // highest marks first; ties keep their order
    });
    int rank = 1;
    for (const auto &s : cls) cout << rank++ << ". " << s.name << " " << s.marks << endl;
    return 0;
}

1. Ravi 95
2. Asha 88
3. Meera 88
4. Kiran 72