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This throws an error id returned 1 error status. The loop is working but I cant print the final concatenated string. When i try to print the final string it does nothing.

char str1[50], str2[50], str[100];
char *p1, *p2, *p3;
int i = 0, j = 0;

p1 = &str1[0];
p2 = &str2[0];
p3 = &str[0];

printf("enter a string:");
gets(str1);

printf("enter a string:");
gets(str2);

while (i <= strlen(str1) + strlen(str2)) {
    if (i != strlen(str1)) {
        *(p3 + i) = *(p1 + i);
        i++;
    } else {
        *(p3 + i) = *(p2 + j);
        j++;
    }
Blaze
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Sanjay Kumar
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1 Answers1

1

This check here is wrong:

if(i!=strlen(str1))

When i is bigger than strlen(str1) it will get false again, but it is supposed to stay true. Change it to this:

if (i < strlen(str1))

Furthermore, you're not increasing i in the else block. This is going to cause an endless loop with ever-growing j, at least until the undefined behavior will cause your program to exit, possibly through an access violation. Try this instead:

else {
    *(p3 + i) = *(p2 + j);
    i++; // increase i in both cases
    j++;
}

Or better yet, make it unconditional. For instance, you could take the i++ out of the body change the loop to this:

for (i = 0; i <= strlen(str1) + strlen(str2); i++)

Also, may I interest you in the array subscript notation? Instead of this:

if (i < strlen(str1)) {
    *(p3 + i) = *(p1 + i);
}

Do this:

if (i < strlen(str1)) {
    p3[i] = p1[i];
}

It's much cleaner this way and people who will work with your code will appreciate it.

Blaze
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    `// increase i in both cases`..rather, make it unconditional. – Sourav Ghosh Apr 25 '19 at 12:44
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    And please do suggest the array subscript notation: `p3[i]` & `p2[j]`. – machine_1 Apr 25 '19 at 12:45
  • @SouravGhosh good idea. I edited the answer to include suggesting a `for` loop with an `i++`, I guess that would be a clean approach. – Blaze Apr 25 '19 at 12:51
  • @machine_1 Great suggestion, added it to the answer. I have to admit, looking at the `*(p3 + i) = *(p1 + i)` construct takes me some time to figure out what's going on. – Blaze Apr 25 '19 at 12:54