hi can anyone help me with my code, im trying to write a bigInt multiply function but this function got some bugs(it prints additional zero at the left side)
input: 3 2
output 06

and ...

#include <cstring>
#include <iostream>
using namespace std;

const int mmax = 10000;

char result[mmax];
void reverse(char* in)
{
int len = strlen(in);
int tail = len - 1;
for(int i = 0; i < len / 2; i++)
{
char temp = in[i];
in[i] = in[tail];
in[tail] = temp;
tail--;

}
}
void multiply(char* first, char* second)
{
char a[mmax], b[mmax];
strcpy(a, first); strcpy(b, second);
int lena = strlen(a);
int lenb = strlen(b);
int lenc = lena + lenb;

reverse(a), reverse(b);

for(int i = 0; i <= lenc; i++)
result[i] = '0';
result[lenc + 1] = '\0';
int i, j;
for(i = 0; i < lenb; i++)
{
int keep = 0;
for(j = 0; j < lena; j++)
{
int res = (a[j] - '0') * (b[i] - '0') + keep + result[i + j] -'0';
keep = res / 10;
result[i + j] = res % 10 + '0';
}
while(keep)
{
int res = result[i + j] - '0' + keep;
result[i + j] = res % 10 + '0';
keep /= 10;
j++;
}
}
int kk;
for(kk = lenc -1  ; i > 0; i--)
{
if(result[kk] != '0')
break;
}
result[kk + 1] = '\0';
reverse(result);
}

int main(void){
char first[mmax], second[mmax];
cin >> first >> second;
multiply(first, second);
cout << result << endl;
return 0;
}

i find my mistake!