void Reverse(string &num)

{

int left=0, right=num.size()-1;

while(left<right)

{

char t=num[left];

num[left]=num[right];

num[right]=t;

left++, right--;

}

}

string multiply(string num1, string num2) {

// Start typing your C/C++ solution below

// DO NOT write int main() function

string ans;

int i, j;

for(i=0;i<num1.size()+num2.size();i++)

ans.push_back('0');

Reverse(num1);

Reverse(num2);

int digit, result;

for(i=0;i<num1.size();i++)

{

digit=0;

for(j=0;j<num2.size();j++)

{

result=(num1[i]-'0')*(num2[j]-'0')+(ans[i+j]-'0')+digit;

digit=result/10;

ans[i+j]=(result%10)+'0';

}

while(digit>0)

{

result=(ans[i+j]-'0')+digit;

digit=result/10;

ans[i+j]=(result%10)+'0';

j++;

}

}

int pos=num1.size()+num2.size()-1;

while(pos>0&&ans[pos]=='0')

pos--;

if(pos<num1.size()+num2.size()-1)

ans.erase(pos+1);

Reverse(ans);

return ans;

}