C++ Arrays

What is an Array?

An array stores multiple values of the same type in a single variable. Elements are stored in contiguous memory.

// Syntax: type name[size] = {values};
int scores[5] = {90, 85, 78, 92, 88};

Accessing Elements

Access by index, starting at 0:

#include <iostream>
using namespace std;

int main() {
    int scores[5] = {90, 85, 78, 92, 88};
    cout << scores[0] << endl;   // 90 (first)
    cout << scores[4] << endl;   // 88 (last)
    scores[2] = 100;              // modify element
    cout << scores[2] << endl;   // 100
    return 0;
}

Looping Through an Array

int nums[] = {10, 20, 30, 40, 50};
int size = sizeof(nums) / sizeof(nums[0]);   // calculate size

for (int i = 0; i < size; i++) {
    cout << nums[i] << " ";
}
// Output: 10 20 30 40 50

// Range-based for (cleaner)
for (int n : nums) {
    cout << n << " ";
}

Multi-Dimensional Arrays

A 2D array is like a table of rows and columns:

int matrix[2][3] = {
    {1, 2, 3},
    {4, 5, 6}
};

for (int i = 0; i < 2; i++) {
    for (int j = 0; j < 3; j++) {
        cout << matrix[i][j] << " ";
    }
    cout << endl;
}

Output:

1 2 3
4 5 6

#include <iostream>
using namespace std;

int main() {
    double temps[] = {36.5, 37.1, 38.0, 35.9, 37.5};
    int n = sizeof(temps) / sizeof(temps[0]);
    double highest = temps[0], lowest = temps[0];

    for (int i = 1; i < n; i++) {
        if (temps[i] > highest) highest = temps[i];
        if (temps[i] < lowest)  lowest  = temps[i];
    }
    cout << "Highest: " << highest << endl;
    cout << "Lowest: "  << lowest  << endl;
    return 0;
}

Summary

• Arrays store multiple values of the same type, indexed from 0.
• Declare: type name[size] = {values};
• Use sizeof(arr)/sizeof(arr[0]) to get array length.
• 2D arrays use two index levels: arr[row][col].