关于在C++代码中使用realloc实现的问题

#include<iostream>
#include <cstdlib>

int main() {
    int* arr = (int*)malloc(10 * sizeof(int));
    for (int i = 0; i < 10; i++) {
        arr[i] = i;
    }
    std::cout << "Before realloc: "<< std::endl;
    for (int i = 0; i < 10; i++) {
        std::cout<< arr[i] << " ";
    }
    std::cout<< std::endl;
    int* newArr = (int*)realloc(arr, 20 * sizeof(int));
    if (newArr == NULL) {
        std::cout << "Realloc failed!"<< std::endl;
        free(arr);
        return 1;
    }
    arr = newArr;
    for (int i = 10; i < 20; i++) {
        arr[i] = i;
    }
    std::cout << "After realloc: "<< std::endl;
    for (int i = 0; i < 20; i++) {
        std::cout<< arr[i] << " ";
    }
    std::cout<< std::endl;
    free(arr);
    return 0;
}