Data Structure and Algorithm

Dynamic Arrays and Memory Allocation

Data Structure and Algorithm 249 views Nov 05, 2025 1 min read

Dynamic Arrays and Memory Allocation

A dynamic array is an array that can automatically resize itself when elements are added or removed. Unlike static arrays, its size is not fixed at compile time.

Key Concept

Dynamic arrays allocate memory on the heap and can grow or shrink as needed. In languages like C++, dynamic arrays are implemented using std::vector. In Java, they are implemented using ArrayList.

How Dynamic Arrays Work

  1. Start with an initial capacity (e.g., 4 elements).
  2. When capacity is full, allocate a new array of double size.
  3. Copy old elements to the new array.
  4. Free the old memory space.

Example (C++ Vector)

#include <vector>
using namespace std;

int main() {
    vector<int> arr;
    arr.push_back(10);
    arr.push_back(20);
    arr.push_back(30);
    return 0;
}

Advantages

  • Resizable – grows automatically as needed.
  • Provides random access like arrays.
  • Efficient insertion at the end.

Disadvantages

  • Copying overhead when resizing.
  • Memory fragmentation due to dynamic allocation.

Applications

  • Used in implementing data structures such as stacks and lists.
  • Used where data size changes frequently during execution.

Conclusion

Dynamic arrays provide flexibility over traditional arrays, making them ideal for applications where the number of elements cannot be determined beforehand.

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