#include <stdio.h> #include <stdlib.h> int main() {     int *ptr = malloc(2 * sizeof(int));  // Allocate memory for 2 integers     if (ptr == NULL) return 1;     ptr[0] = 10;     ptr[1] = 20;     // Resize memory to store 4 integers     int *new_ptr = realloc(ptr, 4 * sizeof(int));     if (new_ptr == NULL) {         free(ptr);         printf("Memory reallocation failed!\n");         return 1;     }     ptr = new_ptr;  // Update pointer reference     ptr[2] = 30;     ptr[3] = 40;     for (int i = 0; i < 4; i++) {         printf("ptr[%d] = %d\n", i, ptr[i]);     }     free(ptr);     ptr = NULL;     return 0; }