create a custom vector struct with manual memory management in swift

To create a custom vector struct with manual memory management in Swift, we need to define a struct that holds a pointer to an array of elements and the size of the array. Here's an example:

main.swift
struct Vector<T> {
    private var elements: UnsafeMutablePointer<T>
    private var size: Int

    init(size: Int) {
        self.elements = UnsafeMutablePointer<T>.allocate(capacity: size)
        self.size = size
    }

    subscript(index: Int) -> T {
        get {
            precondition(index >= 0 && index < size, "Index out of bounds")
            return elements[index]
        }
        set {
            precondition(index >= 0 && index < size, "Index out of bounds")
            elements[index] = newValue
        }
    }

    func deallocate() {
        elements.deallocate()
    }
}
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In this implementation, we use UnsafeMutablePointer to hold a pointer to the memory allocated for the elements array. We also define an init method that takes the size of the vector and allocates memory for the elements array using the allocate method. In addition, we define a subscript method to access the elements of the vector by index safely. Lastly, we define a deallocate method to release the memory used by the vector when it's no longer needed.

Here's an example usage of Vector:

main.swift
let v = Vector<Int>(size: 5)
v[0] = 1
v[1] = 2
v[2] = 3
v[3] = 4
v[4] = 5

print(v[0]) // Output: 1
print(v[4]) // Output: 5

v.deallocate() // Release memory used by vector
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Note that with manual memory management, it's important to use the deallocate method to release the memory used by the vector when it's no longer needed to prevent memory leaks.