public class Solution {
public
String multiply(String num1, String num2) {
int
len1 = num1.length(), len2 = num2.length();
int[] mult = new
int[len1 + len2 + 1];
for(int
i = 0; i < len1 + len2 + 1; ++i)
mult[i] = 0;
for(int
j = 0; j < len1; ++j){
int
carry = 0;
int
singledigit = num1.charAt(len1 - 1
- j) - ‘0‘;
if(singledigit != 0){
for(int
k = 0; k < len2; ++k){
int
product = (num2.charAt(len2 - 1
- k)-‘0‘) * singledigit + carry
+ mult[len1 + len2 - j - k];
mult[len1 + len2 -j - k] = product % 10;
carry = product / 10;
}
if(carry != 0)
mult[len1 - j] = carry;
}
}
StringBuffer sbf = new
StringBuffer();
int
start = 0;
while((start < len1 + len2 + 1) && mult[start] == 0)
++start;
if(start < len1 + len2 + 1){
for(int
i = start; i < len1 + len2 + 1; ++i)
sbf.append(mult[i]);
}
else
sbf.append(‘0‘);
return
sbf.toString();
}
}
