Merge Sort JS …Not able to understand it

Question

 function MergeSortCaller() { let array = [7, 2, 9, 3] const auxiliaryArray = array.slice(); partition (array, 0, array.length - 1, auxiliaryArray); } function partition( mainArray, startIdx, endIdx, auxiliaryArray, ) { if (startIdx === endIdx) return; const middleIdx = Math.floor((startIdx + endIdx) / 2); partition (auxiliaryArray, startIdx, middleIdx, mainArray); partition (auxiliaryArray, middleIdx + 1, endIdx, mainArray); doMerge (mainArray, startIdx, middleIdx, endIdx, auxiliaryArray); } function doMerge( mainArray, startIdx, middleIdx, endIdx, auxiliaryArray, ) { let k = startIdx; let i = startIdx; let j = middleIdx + 1; while (i <= middleIdx && j <= endIdx) { if (auxiliaryArray[i] <= auxiliaryArray[j]) { mainArray[k++] = auxiliaryArray[i++]; } else { mainArray[k++] = auxiliaryArray[j++]; } } while (i <= middleIdx) { mainArray[k++] = auxiliaryArray[i++]; } while (j <= endIdx) { mainArray[k++] = auxiliaryArray[j++]; } console.log(auxiliaryArray, mainArray) } MergeSortCaller()

Output:-

1. Aux -> 7 2 9 3 Main -> 2 7 9 3

2. Aux -> 7 2 9 3 Main -> 2 7 3 9

3. Aux -> 2 7 3 9 Main -> 2 3 7 9

This is working code of Merge Sort. But I am not able to get that how in the 3rd call of doMerge(), the auxilaryArray get changed even I don't make any change to it. In the code all the changes are happening to mainArray. PLZ help me...

Thanks...

Answer 1

Visit Graphical Structure for Visualization of mergesort it may help you.