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.
解题思路一：
BigInteger！！！ JAVA实现如下：
static public String multiply(String num1, String num2) {
java.math.BigInteger bi1=java.math.BigInteger.valueOf(0);
for(int i=0;i<num1.length();i++){
bi1=bi1.multiply(java.math.BigInteger.valueOf(10));
bi1=bi1.add(java.math.BigInteger.valueOf(num1.charAt(i)-‘0‘));
}
java.math.BigInteger bi2=java.math.BigInteger.valueOf(0);
for(int i=0;i<num2.length();i++){
bi2=bi2.multiply(java.math.BigInteger.valueOf(10));
bi2=bi2.add(java.math.BigInteger.valueOf(num2.charAt(i)-‘0‘));
}
return bi1.multiply(bi2).toString();
}
360 ms Accepted，值得注意的是系统不会自动导入math包，需要在声明时添加，不过使用BigInteger总有种作弊的赶脚
Java for LeetCode 043 Multiply Strings
原文：http://www.cnblogs.com/tonyluis/p/4496115.html