class Solution {

    public String multiply(String num1, String num2) {

        if(num1.charAt(0) == '0' || num2.charAt(0) == '0'){

            return "0";

        }

        int len1 = num1.length();

        int len2 = num2.length();

        int len = len1+len2;

        int[] arr = new int[len];

        for(int i=len1-1;i>=0;i--){

            for(int j=len2-1;j>=0;j--){

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

            }

        }

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

            if(arr[i]>=10){

                arr[i-1] += arr[i]/10;

                arr[i]%=10;

            }

        }

        int i=0;

        if(arr[i] == 0) i++;

        String res = "";

        while(i<len){

            res = res+arr[i++];

        }

        return res;

    }

}