| Input: |
| : an unsorted list of length |
| FirstIndex: the first index of to be sorted |
| LastIndex: the last index of to be sorted |
| : top- elements of are to be sorted |
| Output: |
| : Sorted top- elements of ranging from FirstIndex to LastIndex |
| : a stack of pivot positons useful for the afterwards selection sorts |
| (1) if FirstIndex < LastIndex then |
| (2) if !isempty() & top() < LastIndex then /* the stack is available */ |
| (3) pivotpos = pop() /* use the top element of the stack as the pivot */ |
| (4) else |
| (5) /* Partition without using pivots from the stack */ |
| (6) pivotpos=Partition(L, FirstIndex, LastIndex) |
| (7) if pivotpos− FirstIndex +1> then /* The pivot falls after position */ |
| (8) /* The pivot may be useful for the afterwards steps */ |
| (9) push(pivotpos, ) |
| (10) /* QuickSort for top-k in the upper part */ |
| (11) QuickSortTopK(L, FirstIndex, pivotpos −1, k) |
| (12) /* The pivot is located exactly at position */ |
| (13) elseif(pivotpos− FirstIndex +1==) |
| (14) /* QuickSort for top- in the upper part */ |
| (15) QuickSortTopK(L, FirstIndex, pivotpos −1, ) |
| (16) else /* The pivot falls prior to position k */ |
| (17) /* QuickSort the upper part */ |
| (18) QuickSortTopK(L, FirstIndex, pivotpos −1, pivotpos− FirstIndex) |
| (19) /* QuickSort for the residual elements in the lower part */ |
| (20) QuickSortTopK(, pivotpos +1, FirstIndex, -pivotpos+ FirstIndex −1) |
