MergeSortApproach2 is giving stack over flow error

Question

Why this is giving error plz explain
https://code.sololearn.com/c8cH50siB4Fv/?ref=app

Answer 1

in MergeSort()
- because "operator precenence", end/2 was calculate first
//int mid = start + end / 2;
int mid = (start + end) / 2;

- array part can started like mid..end of array
//smallAns[0] = input[0];
smallAns[0] = input[start];

- this change is better (necessary) to get a size 1 element correctly
//int part1[] = MergeSort( input, start, mid-1);
int part1[] = MergeSort( input, start, mid);

//int part2[] = MergeSort( input, mid, input.length-1);
int part2[] = MergeSort( input, mid + 1, end);

- There is a concept conflict ie. return array of size 1
if (start == end) {
int [] smallAns = new int [1];
but the merge() returns the entire input array of fixed size like
part1 [6] + part2 [6] = 12 size,
it attempts merged 12 elements into the input[6]
Instead of a large rewrite of the code I do:

static int[] MergeArrays(int input[], int part1[], int part2[]) {
int i=0, j=0, k=0;
input = new int[part1.length + part2.length]; //added

- then in main() print it like
// MergeSort(input, 0, input.length);
input = MergeSort(input, 0, input.length-1);
PrintArray(input);