C++: تخصيص الذاكرة الديناميكي

Type* pointerName = new Type;

（Program output）

#include <iostream>

int main() {
 // Allocate an int on the heap
 int* p = new int; // p Pointing to int on the heap
 
 *p = 5; // Assign value to int on the heap
 std::cout << "*p = " << *p << std::endl; // 5
 
 return 0;
}

delete pointerName;

#include <iostream>

int main() {
 int* p = new int;
 *p = 5;
 
 std::cout << "*p = " << *p << std::endl;
 
 delete p; // ✅ Free heap memory
 p = nullptr; // ✅ Good practice：Set to nullptr after freeing
 
 return 0;
}

#include <iostream>

void foo() {
 int* p = new int;
 *p = 5;
 // ❌ Forgot to write delete p;
} // Function ends, p is destroyed, but int on heap is not freed (memory leak)

int main() {
 for (int i = 0; i < 1000000; i++) {
 foo(); // Each call leaks 4 bytes
 }
 // Program memory usage keeps growing, may eventually crash
 return 0;
}

Type* pointerName = new Type[size];

#include <iostream>

int main() {
 int n;
 std::cout << "Please enter the array size: ";
 std::cin >> n;
 
 // Allocate an array of n ints on the heap
 int* arr = new int[n];
 
 // Using the array
 for (int i = 0; i < n; i++) {
 arr[i] = i + 1;
 }
 
 // Output the array
 for (int i = 0; i < n; i++) {
 std::cout << arr[i] << " ";
 }
 std::cout << std::endl;
 
 // Free array（Note：Use delete[]，not delete）
 delete[] arr;
 
 return 0;
}

int* p = new int[10];
delete p; // ❌ Error: Should use delete[] p;

#include <iostream>

int main() {
 int* p = new int(5);
 delete p; // Free memory
 
 // ❌ Dangerous: p is now a dangling pointer
 std::cout << *p << std::endl; // Undefined behavior! May output garbage or crash
 
 return 0;
}

delete p;
p = nullptr; // ✅ Good practice

#include <iostream>

// Selection Sort
void selectionSort(int* arr, int n) {
 for (int i = 0; i < n - 1; i++) {
 int minIdx = i;
 for (int j = i + 1; j < n; j++) {
 if (arr[j] < arr[minIdx]) {
 minIdx = j;
 }
 }
 // Swap
 int temp = arr[i];
 arr[i] = arr[minIdx];
 arr[minIdx] = temp;
 }
}

int main() {
 int n;
 std::cout << "Please enter the array size: ";
 std::cin >> n;
 
 int* arr = new int[n]; // Dynamically allocate array
 
 std::cout << "Please enter " << n << " Integer: " << std::endl;
 for (int i = 0; i < n; i++) {
 std::cin >> arr[i];
 }
 
 selectionSort(arr, n); // Sort
 
 std::cout << "After sorting: " << std::endl;
 for (int i = 0; i < n; i++) {
 std::cout << arr[i] << " ";
 }
 std::cout << std::endl;
 
 delete[] arr; // Free memory
 arr = nullptr;
 
 return 0;
}

Please enter the array size: 
Please enter  Integer: 
After sorting: 
 

Please enter the array size: 5
Please enter 5 Integer: 
5 3 1 4 2
After sorting: 
1 2 3 4 5

int* p = new int(5);
delete p;
delete p; // ❌ Error: Double free of same memory (undefined behavior)

delete p;
p = nullptr;

int* arr = new int[10];
// ❌ Forgot to write delete[] arr;

#include <iostream>

int main() {
    int size = 5;
    int* arr = new int[size];

    for (int i = 0; i < size; i++) {
        arr[i] = i * 10;
    }

    for (int i = 0; i < size; i++) {
        std::cout << arr[i] << " ";
    }
    std::cout << std::endl;

    delete[] arr;

    return 0;
}

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