顿搜
飞过闲红千叶，夕岸在哪
类目归类
[LeetCode 43] Multiply Strings[Java]
01/08
1. Description
Given two non-negative integers num1 and num2 represented as strings, return the product of num1 and num2.
Note:
The length of both num1 and num2 is < 110.
Both num1 and num2 contains only digits 0-9.
Both num1 and num2 does not contain any leading zero.
You must not use any built-in BigInteger library or convert the inputs to integer directly.
2. Example
num1 = "13", num2="13"
Output: "169"
3. Code
public class LeetCode0043 {
public String multiply(String num1, String num2) {
if (num1 == null || num1.length() == 0 || num2 == null || num2.length() == 0) {
return "0";
}
int[] sum = new int[num1.length() + num2.length() - 1];
for (int i = num1.length() - 1; i >= 0; i--) {
for (int j = num2.length() - 1; j >= 0; j--) {
sum[i + j] += (num1.charAt(i) - '0') * (num2.charAt(j) - '0');
}
}
StringBuilder sb = new StringBuilder();
int carry = 0;
for (int i = sum.length - 1; i >= 0; i--) {
sum[i] += carry;
carry = sum[i] / 10;
sb.append(sum[i] % 10);
}
while (carry != 0) {
sb.append(carry % 10);
carry /= 10;
}
while (sb.length() > 1 && sb.charAt(sb.length() - 1) == '0') {
sb.deleteCharAt(sb.length() - 1);
}
return sb.reverse().toString();
}
public static void main(String[] args) {
LeetCode0043 leetcode = new LeetCode0043();
System.out.println(leetcode.multiply("13", "13"));
}
}
