UVa10579 Fibonacci Numbers

#include <stdio.h>
#include <string.h>
#define MAX 1000
void reverse(char *from, char *to);
void call_add(char *first, char *second, char *result);
int main()
{
char f[MAX], s[MAX], r[MAX];
int n;
int i;
while (scanf("%d", &n) != EOF) {
if (n == 1)
printf("1\n");
else if (n == 2)
printf("1\n");
else {
strcpy(f, "1");
strcpy(s, "1");
for (i = 2; i < n; i++) {
call_add(f, s, r);
strcpy(f, s);
strcpy(s, r);
}
printf("%s\n", s);
}
}
return 0;
}
void reverse(char *from, char *to)
{
int i, len = strlen(from);
for (i = 0; i < len; i++)
to[i] = from[len ‐ 1 ‐ i];
to[len] = '\0';
}
void call_add(char *first, char *second, char *result)
{
char F[MAX], S[MAX], Res[MAX];
int f_len, s_len, i, carry;
int sum;
f_len = strlen(first);
s_len = strlen(second);
reverse(first, F);
reverse(second, S);
for (i = 0, carry = 0; i < f_len && i < s_len; i++) {
sum = (F[i] ‐ '0') + (S[i] ‐ '0') + carry;
Res[i] = sum % 10 + '0';
carry = sum / 10;
}
for (; i < f_len; i++) {
sum = (F[i] ‐ '0') + carry;
Res[i] = sum % 10 + '0';
carry = sum / 10;
}
for (; i < s_len; i++) {
sum = (S[i] ‐ '0') + carry;
Res[i] = sum % 10 + '0';
carry = sum / 10;
}
if (carry)
Res[i++] = '0' + carry;
Res[i] = '\0';
reverse(Res, result);
}