C++ Arrays, Vectors and Strings Practice

Practise std::vector, std::array, std::string, 2D grids and structs with common collection tasks.

Beginner7 problemsUpdated October 23, 2026

Review first: Arrays, Vectors, Strings, 2D Arrays and Grids, Structs and Enums

1.Marks statistics

Beginner

Given std::vector<int> marks = {56, 91, 78, 34, 88};, print the total, the average (as a decimal) and the highest mark.

Show hint

One range-based for loop can add up the total and track the highest value at the same time.

Show solution

C++

#include <iostream>
#include <vector>

int main() {
    std::vector<int> marks = {56, 91, 78, 34, 88};

    int total = 0;
    int highest = marks[0];
    for (int m : marks) {
        total += m;
        if (m > highest) highest = m;
    }

    std::cout << "Total: " << total << '\n';
    std::cout << "Average: " << static_cast<double>(total) / marks.size() << '\n';
    std::cout << "Highest: " << highest << '\n';
}

Output

Total: 347
Average: 69.4
Highest: 91

2.Reverse a string in place

Beginner

Reverse std::string word = "algorithm"; in place by swapping characters from both ends, without std::reverse.

Show hint

Use two indexes, one from the start and one from the end, and swap until they meet.

Show solution

C++

#include <iostream>
#include <string>
#include <utility>

int main() {
    std::string word = "algorithm";

    std::size_t i = 0;
    std::size_t j = word.size() - 1;
    while (i < j) {
        std::swap(word[i], word[j]);
        ++i;
        --j;
    }
    std::cout << word << '\n';
}

Output

mhtirogla

3.Count the vowels

Beginner

Count the vowels (a, e, i, o, u, either case) in "Programming In C++ Is Fun".

Show hint

Convert each character with std::tolower (from <cctype>) and check it against "aeiou" with std::string::find.

Show solution

C++

#include <cctype>
#include <iostream>
#include <string>

int main() {
    std::string text = "Programming In C++ Is Fun";
    const std::string vowels = "aeiou";

    int count = 0;
    for (char c : text) {
        char lower = static_cast<char>(std::tolower(static_cast<unsigned char>(c)));
        if (vowels.find(lower) != std::string::npos) ++count;
    }
    std::cout << count << '\n';
}

Output

4.Palindrome check

Beginner

Write bool is_palindrome(const std::string& s) and print the result for "racecar" and "rocket".

Show hint

Compare the string with a reversed copy, built from s.rbegin() and s.rend().

Show solution

C++

#include <iostream>
#include <string>

bool is_palindrome(const std::string& s) {
    return s == std::string(s.rbegin(), s.rend());
}

int main() {
    std::cout << std::boolalpha << is_palindrome("racecar") << ' ' << is_palindrome("rocket") << '\n';
}

Output

true false

5.Row and column totals

Beginner

For the grid {{3, 1, 4}, {1, 5, 9}, {2, 6, 5}}, print the total of each row, then the total of each column.

Show hint

For column totals, put the column loop on the outside.

Show solution

C++

#include <iostream>
#include <vector>

int main() {
    std::vector<std::vector<int>> grid = {{3, 1, 4}, {1, 5, 9}, {2, 6, 5}};

    for (const auto& row : grid) {
        int sum = 0;
        for (int v : row) sum += v;
        std::cout << sum << ' ';
    }
    std::cout << '\n';

    for (std::size_t c = 0; c < grid[0].size(); ++c) {
        int sum = 0;
        for (std::size_t r = 0; r < grid.size(); ++r) sum += grid[r][c];
        std::cout << sum << ' ';
    }
    std::cout << '\n';
}

Output

8 15 13
6 12 18

6.Remove duplicates, keep order

Beginner

Build a new vector from {4, 9, 4, 1, 9, 9, 7} that keeps only the first occurrence of each value, in the original order.

Show hint

Before adding a value, check whether it is already in the result with std::find.

Show solution

C++

#include <algorithm>
#include <iostream>
#include <vector>

int main() {
    std::vector<int> data = {4, 9, 4, 1, 9, 9, 7};
    std::vector<int> unique;

    for (int x : data) {
        if (std::find(unique.begin(), unique.end(), x) == unique.end()) {
            unique.push_back(x);
        }
    }
    for (int x : unique) std::cout << x << ' ';
    std::cout << '\n';
}

Output

4 9 1 7

7.Inventory value

Beginner

Define struct Product { std::string name; double price; int stock; };. For the products {"Pen", 25, 120}, {"Notebook", 60, 0} and {"Bag", 799, 4}, print the names of out-of-stock products and the total stock value.

Show hint

Loop over a std::vector<Product> by const&; the value of one product is price * stock.

Show solution

C++

#include <iostream>
#include <string>
#include <vector>

struct Product {
    std::string name;
    double price = 0;
    int stock = 0;
};

int main() {
    std::vector<Product> products = {{"Pen", 25, 120}, {"Notebook", 60, 0}, {"Bag", 799, 4}};

    double value = 0;
    for (const Product& p : products) {
        if (p.stock == 0) std::cout << p.name << " is out of stock\n";
        value += p.price * p.stock;
    }
    std::cout << "Total value: " << value << '\n';
}

Output

Notebook is out of stock
Total value: 6196

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