leetcode--Multiply Strings

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.

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public class Solution {  

    public String multiply(String num1, String num2) {  

        int[] res = new int[num1.length()+num2.length()];  

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

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

                int n1 = num1.charAt(i)-'0';  

                int n2 = num2.charAt(j)-'0';  

                res[i+j+1] += n1*n2;  

            }  

        }  

        int flag = 0;         

        for(int i=res.length-1;i>=0;i--){  

            int tmp = (res[i] + flag) % 10;  

            flag = (res[i] + flag) / 10;  

            res[i] = tmp;  

        }  

        StringBuilder sb = new StringBuilder();  

        for (int num : res) sb.append(num);  

        while (sb.length() != 0 && sb.charAt(0) == '0') sb.deleteCharAt(0);  

        return sb.length() == 0 ? "0" : sb.toString();  

    }  

}  



原文链接http://blog.csdn.net/crazy__chen/article/details/45752001