C program to concatenate two strings using pointer

#include<stdio.h>
int main()
{
    char str1[50], str2[50];
    char * p1 = str1;
    char * p2 = str2;
    printf("Enter first string: ");
    gets(str1);
    printf("Enter second string: ");
    gets(str2);
    /* increment till the end of str1 */
    while(*(++p1));
    // Coping str2 to str1
    while(*(p1++) = *(p2++));
    printf("Concatenated two string are: %s", str1);
    return 0;
}

#include<stdio.h>
int main()
{
    char a1[20],a2[20],c[30];
    int i,j;
    char *p1,*p2,*p3;
    p3=c;
    p1=a1;
    p2=a2;
    printf("enter first string:");
    gets(p1);
    printf("enter second string:");
    gets(p2);
    for(i=0;*(p1+i)!='\0';i++)
    {
       *(p3+i)=*(p1+i);
    }
    for(j=0;*(p2+j)!='\0';j++,i++)
    { *(p3+i)=*(p2+j); }
    *(p3+i)='\0';
    printf("after concating two string: %s",p3);
    return 0;
}