Array index out of bounds

Question

Although I tried to solve the exception using break it still fails on the input "321". Code for bubble sort on hackerrank.

The error occurs on if(a[i+1]==n).

import java.io.*;``
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    int n = in.nextInt();
    int[] a = new int[n];
    for(int a_i=0; a_i < n; a_i++){
        a[a_i] = in.nextInt();
    }
    // Write Your Code Here
    int numSwaps=0;
    for(int i=0;i<n;i++){
        if(a[i+1]==n){       // error occurs here
            break;
        }
        else{
                if(a[i]>a[i+1]){
                int temp=a[i];
                a[i]=a[i+1];
                a[i+1]=temp;
                numSwaps++;
                }
            }
    }
    //firstElement=a[0];
    //lastElement=a[n-1];
    System.out.println("Array is sorted in"+" "+numSwaps+" "+"swaps."+"\n"+"First Element:"+" "+a[0]+"\n"+"Last Element:"+" "+a[n-1]);
}

}

Answer 1

Your condition i<n will overflow when i=n-1, because you are adding i+1, you are referencing the array out-of-bounds.

The fix is easy, however, change the condition to i<n-1.

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] a = new int[n];
        for(int a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
        }
        // Write Your Code Here
        int numSwaps=0;
        for(int i=0;i<n-1;i++){
            if(a[i+1]==n){
                break;
            } else if(a[i]>a[i+1]){
                int temp=a[i];
                a[i]=a[i+1];
                a[i+1]=temp;
                numSwaps++;
            }
        }
        //firstElement=a[0];
        //lastElement=a[n-1];
        System.out.println("Array is sorted in"+" "+numSwaps+" "+"swaps."+"\n"+"First Element:"+" "+a[0]+"\n"+"Last Element:"+" "+a[n-1]);
}

Also, take bit of pride in code style; I did a couple touch-ups, but its far from clean.