/**

*Given two numbers represented as strings, return multiplication of the numbers as a string.

*Note:The numbers can be arbitrarily large and are non-negative.

*Converting the input string to integer is NOT allowed.

*You should NOT use internal library such as BigInteger.

*/

class Solution {

public:

string multiply(string num1, string num2) {

string res(num1.size()+num2.size(),'0');

for(int i = num1.size()-1; i >= 0; i--)

{

int carry = 0;

for(int j = num2.size()-1; j >= 0; j--)

{

int temp = res[i+j+1] - '0' +(num1[i] - '0')*(num2[j]-'0')+carry;

res[i+j+1] = temp%10 + '0';

carry = temp/10;

}

res[i] = res[i] - '0' + carry +'0';

}

size_t startpos = res.find_first_not_of("0");

if (string::npos != startpos) {

return res.substr(startpos);

}

return "0";

}

};