Dynamic string size

// Example program
#include <stdio.h>
#include <string>
#include <stdlib.h>
using namespace std;
int main()
{
  int sizeOfString = 0;
  printf("Enter size: \n");
  scanf("%d", &sizeOfString);

  char* string = (char*)malloc(sizeOfString);
  for(int i =0; i<sizeOfString; i++)
  {
      string[i] = rand()%26+'a';
  }
  string[sizeOfString] = 0;
  printf("%s\n", string);
  int stringSize = sizeof(string);
  printf("size of string %d \n", stringSize);

  return 0;
}