MergeSort implementions out of bounds-CodePudding

import java.util.Arrays;

class MergeSort {
    public static int[] merge(int[] left, int[] right) {
        // Initial indexes of first and second subarrays
        int[] arr = new int[left.length   right.length];
        int countLeft = 0;
        int countRight = 0;
            
        // TODO Complete the method
        while (countLeft < left.length && countRight < right.length) {
            if (left[countLeft] < right[countRight]) {
                arr[countLeft] = left[countLeft];
                countLeft  ;
            } else {
                arr[countRight] = left[countRight];
                countRight  ;
            }
        }
        while (countLeft < left.length) {
            arr[countLeft] = left[countLeft];
            countLeft  ;
        }
        while (countRight < right.length) {
            arr[countRight] = left[countRight];
            countRight  ;
        }
        return arr;
    }
            
    public static int[] sort(int arr[]) {
        // Find the middle point
        if (arr.length > 1) {
            int m = arr.length / 2;
            int[] l1 = Arrays.copyOfRange(arr, 0, m);
            int[] l2 = Arrays.copyOfRange(arr, m, arr.length);
            
            l1 = sort(l1);
            l2 = sort(l2);
                        
            return merge(l1, l2);
        } else {
            return arr;
        }
    }
            
    public static void main(String[] args) {
        int [] arr = {1, 6, 64, 3, 7, 3, 7};
        //                sort(arr);
        MergeSort ob = new MergeSort();
        ob.sort(arr);
        System.out.println(Arrays.toString(arr));
    }
}

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 1 out of bounds for length 1
                at um.MergeSort.merge(MergeSort.java:28)
                at um.MergeSort.sort(MergeSort.java:44)
                at um.MergeSort.sort(MergeSort.java:41)
                at um.MergeSort.main(MergeSort.java:55)

Anyone knows why I have the out of bounds? (I know what out of bounds means, I just don't know why I have it).

According to this is should be a out of bounds in line 28 which correspond with arr[countRight] = left[countRight]; but why?

CodePudding user response：

This looks like a copy and paste error to me. I believe you meant:

arr[countRight] = right[countRight];

CodePudding user response：

you need to change your merge method implementation. in the third while of the merge method, you should fill arr[] with the right array.

public static int[] merge(int[] left, int[] right) {
    // Initial indexes of first and second subarrays
    int[] arr = new int[left.length   right.length];
    int countLeft = 0;
    int countRight = 0;
   

    // TODO Complete the method
    while (countLeft < left.length && countRight < right.length) {
        if (left[countLeft] < right[countRight]) {
            arr[countLeft] = left[countLeft];
            countLeft  ;
          
        } else {
            arr[countRight] = right[countRight];
            countRight  ;
        
        }
    }
    while (countLeft < left.length) {
        arr[countLeft] = left[countLeft];
        countLeft  ;
    
    }
    while (countRight < right.length) {
        arr[countRight ] = right[countRight];
        countRight  ;
      
    }
    return arr;
}