Revise paste NCTU LAB 07/05 NUM 2

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

#define MAX 20

void reverseCopy(char *from, char *to){
	int length = strlen(from);
	for(int i=0;i<length;i++){
		to[i] = from[length-i-1];
	}
	to[length]='\0';
}

void mult(char *first, char *sec, char *result){
	char F[MAX],S[MAX],temp[MAX];
	int i, j, r, t_len, carry, res;
	int f_len = strlen(first);
	int s_len = strlen(sec);
	reverseCopy(first,F);
	reverseCopy(sec,S);
	t_len = f_len+s_len;
	r = -1;
	for(i=0;i<=t_len;i++){
		temp[i] = '0';
	}
	temp[i]='\0';
	for(j=0;j<s_len;j++){
			carry = 0;
			for(i=0;i<f_len;i++){
				res = (F[i]-'0') * (S[j] - '0') + carry + (temp[i+j] - '0');
				temp[i+j] = res%10 + '0';
				carry = res/10;
				if(i+j > r){
					r = i + j;
				}
			}
			while(carry!=0){
				res = carry + temp[i+j] - '0';
				carry = res/10;
				temp[i+j] = res%10 + '0';
				if(i+j > r){
					r = i + j;
				}
				i++;
			}
		}
		for(;r>0 && temp[r]=='0';r--);
		temp[r+1]='\0';
		reverseCopy(temp,result);
}
	
int main(){
	char first[MAX], second[MAX], res[MAX];
	while(scanf("%s%s", &first, &second)){
		mult(first, second, res);
		int len = strlen(res);
		printf("Result : ");
		for(int i=0;i<len;i++){
			printf("%c", res[i]);
		}
		printf("\n");
}
return 0;
}