// 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.

public class Solution {

public String multiply(String num1, String num2) {

int m = num1.length();

int n = num2.length();

int[] pos = new int[m + n];

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

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

int mul = (num1.charAt(i) - '0') * (num2.charAt(j) - '0');

int p1 = i + j;

int p2 = i + j + 1;

int sum = mul + pos[p2];

pos[p1] += sum / 10;

pos[p2] = (sum) % 10;

}

}

StringBuilder sb = new StringBuilder();

for(int p : pos) if(!(sb.length() == 0 && p == 0)) sb.append(p);

return sb.length() == 0 ? "0" : sb.toString();

}

}