Pointer Arithmetic

Overview

Pointer arithmetic allows you to add or subtract integers from pointers to navigate through contiguous memory blocks, like arrays. It moves by the size of the data type.

Syntax

cpp

int arr[3] = {10, 20, 30};
int* ptr = arr;

cout << *ptr;       // 10
ptr++;              // Move to next int (adds 4 bytes to address)
cout << *ptr;       // 20
cout << *(ptr + 1); // 30

Common Pitfalls

Using pointer arithmetic on pointers that don't point to arrays. Moving past a single isolated variable points to garbage memory.

Interview Tips

Explain exactly what `ptr++` does. If `ptr` is an `int*` pointing to address `1000`, `ptr++` changes it to `1004` (assuming int is 4 bytes). It does NOT change to `1001`.

Real-World Example

Traversing an array strictly using pointer arithmetic.

example

cpp

#include <iostream>
using namespace std;

int main() {
    int arr[] = {10, 20, 30, 40};
    int* ptr = arr;
    
    // Iterate 4 times
    for (int i = 0; i < 4; i++) {
        cout << *ptr << " ";
        ptr++; // Advance the pointer
    }
    return 0;
}

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