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system
write pseudocode for a merge sort algorithm.
user
mergesort(a, startindex, endindex):
    // if there is only one element in the array, return
    if startindex == endindex:
        return

    middleindex = (startindex + endindex) / 2

    // sort the left half of the array
    mergesort(a, startindex, middleindex)

    // sort the right half of the array
    mergesort(a, middleindex + 1, endindex)

    // merge the two sorted arrays
    merge(a, startindex, endindex)

merge(a, startindex, endindex):
    middleindex = (startindex + endindex) / 2
    leftindex = startindex
    rightindex = middleindex + 1

    // temporary array to hold the sorted array
    temparray[]

    // iterate through both halves of the array
    for i in range(startindex, endindex+1):
        // if left half is done iterating, add from right half
        if leftindex > middleindex:
            temparray[i] = a[rightindex]
            rightindex++

        // if right half is done iterating, add from left half
        else if rightindex > endindex:
            temparray[i] = a[leftindex]
            leftindex++

        // compare current element and add the smaller element
        else if a[leftindex] < a[rightindex]:
            temparray[i] = a[leftindex]
            leftindex++
        else:
            temparray[i] = a[rightindex]
            rightindex++

    // copy the temparray back to a
    for i in range(startindex, endindex+1):
        a[i] = temparray[i]
assistant