package com.github.jerring.leetcode;

public class LeetCode_00043 {

public String multiply(String num1, String num2) {

if (num1.equals("0") || num2.equals("0")) {

return "0";

}

int n1 = num1.length();

int n2 = num2.length();

int[] arr = new int[n1 + n2 - 1];

for (int i = n1 - 1; i >= 0; --i) {

for (int j = n2 - 1; j >= 0; --j) {

arr[arr.length - 1 - i - j] += (num1.charAt(i) - '0') * (num2.charAt(j) - '0');

}

}

StringBuilder sb = new StringBuilder();

int carry = 0;

for (int i = 0; i < arr.length || carry != 0; ++i) {

carry += i < arr.length ? arr[i] : 0;

sb.append(carry % 10);

carry /= 10;

}

return sb.reverse().toString();

}

}