ModAdd

// A Sample Java program for beginners with Competitive Programming
import java.util.*;
import java.lang.*;
import java.io.*;

class ModAdd
{
    // This function returns index of element x in arr[]
    static String modAdd(String as, String bs)
    {
        int al=as.length();
        int bl=bs.length();
        int length=al>bl?al:bl;

        int offset =0;
        String result="";
        for(offset=0;offset<length;offset++){
            if(al>offset && bl>offset){
                int c = (as.charAt(al-offset-1)-'0' + bs.charAt(bl-offset-1) -'0')%10;
                result = c + result;
            } else {
                break;
            }
        }
        if(al>offset){
            result = as.substring(0,al-offset) + result;
        } else if(bl>offset){
            result = as.substring(0,bl-offset) + result;
        }

        while(result.startsWith("0")){
            if(result.length()==1){
                break;
            }
            result = result.substring(1);
        }
        return result;

    }

    public static void main (String[] args)
    {
        // Note that size of arr[] is considered 100 according to
        // the constraints mentioned in problem statement.

        IO io = new IO();

        //String a = io.next(); // Reads the next string separated by spaces.
        String a = io.next(); // Reads the next int separated by spaces.
        String b = io.next(); // Reads the next int separated by spaces.
        //long c = io.nextLong(); // Reads the next long separated by spaces.
        //double d = io.nextDouble(); // Reads the next double separated by spaces.


        io.println(modAdd(a,b));
        io.close(); // MUST BE CALLED IN THE END, otherwise some of the output may be missing
    }
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: TIME LIMIT EXCEEDED

Test 4

Verdict: RUNTIME ERROR

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 999999
	at java.lang.String.substring(String.java:1963)
	at ModAdd.modAdd(ModAdd.java:28)
	at ModAdd.main(ModAdd.java:55)

Test 5

Verdict: RUNTIME ERROR

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 999999
	at java.lang.String.substring(String.java:1963)
	at ModAdd.modAdd(ModAdd.java:28)
	at ModAdd.main(ModAdd.java:55)

Test 6

Verdict: ACCEPTED

Test 7

Verdict: TIME LIMIT EXCEEDED

Test 8

Verdict: TIME LIMIT EXCEEDED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: TIME LIMIT EXCEEDED