C - Adding the numbers in 2 strings together if a different length -

if had 2 strings:

a = "1234" b = "4321" 

i add 2 numbers this:

for(i=0; i<width-1; i++){     sum = (a[width-2-i]-48) + (b[width-2-i]-48) + carry;     carry = 0;     if(sum > 9){         carry = 1;         sum-=10;     }     answer[i] = sum+48; }  if(carry) answer[i++] = carry+48; answer[i]= 0; 

and reverse (width equal strlen(a)).

how same thing if following?

a = "12345" b = "4321" 

would need reallocate memory? or what?

(btw - the problem i'm trying solve using many numbers 50 digits, strtoul or strtoull out of question understand. here's code far.)

int getcharval(const char *s, int idx) {     if (idx < strlen(s))         return s[strlen(s) - idx - 1] - 48;      return 0; }  void add() {     const char *a = "1234";     const char *b = "13210";     char answer[256];     int i, wa=strlen(a), wb=strlen(b), width, sum, carry;     width = wa > wb ? wa : wb;      for(i=0; i<width; i++){         char ca = getcharval(a, i);          char cb = getcharval(b, i);          printf("%d %d\n", ca, cb);         sum = ca + cb + carry;         carry = 0;         if(sum > 9){              carry = 1;             sum-=10;         }         answer[i] = sum+48;     }        if(carry) answer[i++] = carry+48;     answer[i]= 0;     (i = 0; < strlen(answer) / 2; i++) {         char t = answer[i];         answer[i] = answer[strlen(answer) - - 1];          answer[strlen(answer) - - 1] = t;     }         printf("%s\n", answer); }