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.
代码语言：javascript复制 public String multiply(String num1, String num2) {
if (num1 == null || num2 == null) {
return "";
}
int[] paper = new int[num1.length() num2.length()];
char[] _num1 = num1.toCharArray();
char[] _num2 = num2.toCharArray();
for (int i = 0; i < _num1.length; i ) {
for (int j = 0; j < _num2.length; j ) {
paper[paper.length - (i j 2)] = (_num1[i] - '0')
* (_num2[j] - '0');
}
}
// add
for (int i = 0; i < paper.length - 1; i ) {
paper[i 1] = paper[i] / 10;
paper[i] %= 10;
}
String s = "";
for (int i = paper.length - 1; i > 0; i--) {
if ("" == s && paper[i] == 0) {
continue;
}
s = paper[i];
}
s = paper[0];
return s;
}
// can't be accepted in leetcode
public String multiply2(String num1, String num2) {
if (num1 == null || num2 == null) {
return "";
}
BigInteger n1 = new BigInteger(num1);
BigInteger n2 = new BigInteger(num2);
return n1.multiply(n2).toString();
}
