BigInt add

刚刚面完第二轮电面，原题 BigInt, 不过把详细一点的放在这里，和我的答案。// This is the text editor interface. 
// Anything you type or change here will be seen by the other person in real time.
. more info on 1point3acres.com
/*
* class BigInt, to represent non-negative integers of arbitrary size
        * constructor accept a String, representing this non-neg int (e.g. "50"), assume valid input    . visit 1point3acres.com for more.
        * needs to be able to add to another BigInt, and return their sum as a new BigInt object
        * immutable
            * new BigInt("20").add(new BigInt("30")) --> BigInt("50")

import java.util.Random;

public class Solution {

public String add(String str1, String str2) {

StringBuilder sb = new StringBuilder();

int i1 = str1.length() - 1;

int i2 = str2.length() - 1;

int carry = 0;

int base = 10;

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

int val = carry;

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

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

carry = val / base;

sb.append(val % base);

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.add(Integer.toString(n1), Integer.toString(n2));

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

}

}