leetcode 82: Multiply String

Multiply StringsMar 12 '12

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.

uncompleted

 

 

public class Solution {
    public String multiply(String num1, String num2) {
        // Start typing your Java solution below
        // DO NOT write main() function
        int sz1 = num1.length();
        int sz2 = num2.length();
        
        if(sz1<1 || sz2<1) return new String();
        
        
        char[] res = new char[sz1+sz2];
        
        int  carry =0;
        for(int i=sz1-1; i>=0; i--) {
            char c = num1.charAt(i);
            carry =0;
            int k=i+sz2;
            
            for(int j=sz2-1; j>=0; j--) {
                int t = (c-'0') * (num2.charAt(j)-'0') + carry;
                if(res[k]!=0) t += res[k]-'0';
                carry = t/10;
                res[k--] = (char)(t%10 + '0');
            }
            if(carry!=0) 
            res[k] = (char)(carry + '0');
        }
        
        if(carry!=0) {
            res[0] = (char)(carry + '0');
            return new String(res);
        } else {
            
             return new String(res,1,res.length-1);
        }
    }
}