bigint subtract

bigint subtract

import java.util.Random;

public class Solution {

public String sub(String str1, String str2) {

if (str1.length() < str2.length() || (str1.length() == str2.length() && str1.compareTo(str2) < 0)) {

return "-" + sub(str2, str1);

}

StringBuilder sb = new StringBuilder();

int i1 = str1.length() - 1;

int i2 = str2.length() - 1;

int carry = 0;

while (i1 >= 0 || i2 >= 0) {

int val = -carry;

val += i1 >= 0 ? (str1.charAt(i1) - '0') : 0;

val -= i2 >= 0 ? (str2.charAt(i2) - '0') : 0;

if (val < 0) {

carry = 1;

val += 10;

} else {

carry = 0;

}

sb.append(val);

i1--;

i2--;

}

return sb.reverse().toString();

}

public static void main(String args[]) {

Solution s = new Solution();

Random r = new Random();

int n1 = r.nextInt(100000000);

int n2 = r.nextInt(100000000);

String n3 = s.sub(Integer.toString(n1), Integer.toString(n2));

System.out.println((n1 + "-" + n2) + "=" + (n1 - n2) + "=" + Integer.parseInt(n3));

}

}