Unit 2: Arrays, strings and data structures

An array is a collection of elements of the same type stored in consecutive memory locations under one name. Elements are accessed by an index starting from 0.

• One-dimensional: int marks[5] = {70, 82, 65, 90, 77}; — marks[0] is 70.
• Two-dimensional (matrix): int a[3][3]; — a[i][j] is row i, column j.
• Passing an array to a function passes the address of its first element, so the function works on the original array: void display(int a[], int n);

c/* Largest element of an array */
int max = a[0];
for (int i = 1; i < n; i++)
    if (a[i] > max) max = a[i];

c/* Matrix addition and multiplication */
int a[2][2] = {{1, 2}, {3, 4}}, b[2][2] = {{5, 6}, {7, 8}}, c[2][2] = {0};
for (int i = 0; i < 2; i++)
    for (int j = 0; j < 2; j++)
        for (int k = 0; k < 2; k++)
            c[i][j] += a[i][k] * b[k][j];   /* c = {{19, 22}, {43, 50}} */

• Row-major storage: element a[i][j] of an m × n array is at base + (i × n + j) × size.
• Common programs: addition, multiplication (columns of A = rows of B), transpose, sum of diagonals, checking symmetry.

A string is an array of characters ending with the null character '\0'. char name[10] = "SBS"; uses 4 bytes ('S', 'B', 'S', '\0').

cpp#include <string>
#include <algorithm>
string s = "Synetic";
s += " Business School";                    // concatenation
cout << s.length() << ' ' << s.substr(0, 7) << ' ' << s.find("School") << '\n';
s.replace(0, 7, "SBS");
reverse(s.begin(), s.end());
string a = "apple", b = "banana";
cout << (a < b) << ' ' << a.compare(b) << '\n';     // lexicographic comparison
for (char &c : a) c = toupper(c);                     // APPLE

• The string class manages memory automatically and supports =, +, ==, <, [] and methods such as length, substr, find, insert, erase, replace — safer than char arrays.

• In C++ a struct can contain member functions and access specifiers; members are public by default (in a class they are private by default).
• Unions share memory among members; C++ unions can have member functions; anonymous unions allow direct member access.

cppstruct Point {
    int x, y;
    void show() { std::cout << "(" << x << ", " << y << ")\n"; }
};