Week 6 Syntax Guide

Passing Arrays to Functions

When passing an array to a function, the array “decays” into a pointer to its first element. Changes inside the function affect the original array.

Syntax:

// Function Prototype
void functionName(dataType arrayName[], int size);

// Function Call
functionName(actualArray, size);

Example:

void printArray(int arr[], int size) {
    for (int i = 0; i < size; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");
}

int main() {
    int nums[5] = {1, 2, 3, 4, 5};
    printArray(nums, 5); // Pass array name and size
    return 0;
}

void printArray(int arr[], int size) {
    for (int i = 0; i < size; i++) {
        cout << arr[i] << " ";
    }
    cout << "\n";
}

int main() {
    int nums[5] = {1, 2, 3, 4, 5};
    printArray(nums, 5); // Pass array name and size
    return 0;
}

Searching Algorithms

Iterates through the array to find a specific key. Works on unsorted arrays.

Syntax:

int linearSearch(int arr[], int size, int key) {
    for (int i = 0; i < size; i++) {
        if (arr[i] == key) {
            return i; // Return index if found
        }
    }
    return -1; // Return -1 if not found
}

Divides the search interval in half. Requires a sorted array.

Syntax:

int binarySearch(int arr[], int size, int key) {
    int low = 0, high = size - 1;
    
    while (low <= high) {
        int mid = low + (high - low) / 2;
            
        if (arr[mid] < key)
            low = mid + 1; // Ignore left half
        else if (arr[mid] > key)
            high = mid - 1; // Ignore right half
        else
            return mid; // Match found
    }
    
    return -1; // Not found
}

Common Array Algorithms

Reversing an Array

Swaps elements from both ends moving towards the center.

Syntax:

void reverseArray(int arr[], int size) {
    int start = 0, end = size - 1;
    while (start < end) {
        int temp = arr[start];
        arr[start] = arr[end];
        arr[end] = temp;
        start++;
        end--;
    }
}

Rotating an Array

Moves elements to the right or left, wrapping around.

Rotate Right:

void rotateRight(int arr[], int size) {
    int last = arr[size - 1];
    for (int i = size - 1; i > 0; i--) {
        arr[i] = arr[i - 1];
    }
    arr[0] = last;
}

Rotate Left:

void rotateLeft(int arr[], int size) {
    int first = arr[0];
    for (int i = 0; i < size - 1; i++) {
        arr[i] = arr[i + 1];
    }
    arr[size - 1] = first;
}