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| -rw-r--r-- | csci1913/Java/project2_strap012.java | 140 |
1 files changed, 140 insertions, 0 deletions
diff --git a/csci1913/Java/project2_strap012.java b/csci1913/Java/project2_strap012.java new file mode 100644 index 0000000..4010657 --- /dev/null +++ b/csci1913/Java/project2_strap012.java @@ -0,0 +1,140 @@ +// SORT. Sort a linear singly-linked list of INTs. + +class Sort { + + // NODE. A node in a linear singly linked list of INTs. + + private static class Node { + private int number; // The INT in the node, duh. + private Node next; // The NODE that follows this one, or NULL. + + // Constructor. Initialize a new NODE with NUMBER and NEXT. + + private Node(int number, Node next) { + this.number = number; + this.next = next; + } + } + + // MAKE NODES. Return a list of NODEs that contains INTs from NUMBERS in order + // of their appearance. + + private static Node makeNodes(int... numbers) { + if (numbers.length > 0) { + Node first = new Node(numbers[0], null); + Node last = first; + for (int index = 1; index < numbers.length; index += 1) { + last.next = new Node(numbers[index], null); + last = last.next; + } + return first; + } else { + return null; + } + } + + // WRITE NODES. Write the INTs from a list of NODEs in paired square brackets, + // separated by commas, with a newline at the end. + + private static void writeNodes(Node nodes) { + System.out.print('['); + if (nodes != null) { + System.out.print(nodes.number); + nodes = nodes.next; + while (nodes != null) { + System.out.print(", "); + System.out.print(nodes.number); + nodes = nodes.next; + } + } + System.out.println(']'); + } + + // SORT NODES. Sort UNSORTED, a list of NODEs, into nondecreasing order of its + // NUMBER slots, without making new NODEs. + + private static Node sortNodes(Node unsorted) { + Node left=null, right=null, sorted=null; + boolean firstSort=true; + if (unsorted==null || unsorted.next==null) { + //unsorted list is either empty or of length 1 + return unsorted; + } else { + //--HALVING PHASE-- + int oddeven = 0; + boolean firstNodeR = true, firstNodeL = true; + while (unsorted!=null) { + + if (oddeven%2==0) { + if (firstNodeL) { + left=unsorted; + firstNodeL=false; + } else { + unsorted=left.next; + } + } else { + if (firstNodeR) { + right=unsorted; + firstNodeR=false; + } else { + unsorted = right.next; + } + } + oddeven++; + unsorted=unsorted.next; + } + } + //--SORTING PHASE-- + sortNodes(left); sortNodes(right); + //--COMBINING PHASE + while (left != null || right != null) { + if (left.number>right.number) { + if(firstSort) { + sorted = left; + firstSort = false; + } else { + sorted.next = left; + } + left = left.next; + } else { + if (firstSort) { + sorted = right; + firstSort = false; + } else { + sorted.next = right; + } + right = right.next; + } + } + if (left==null) { + while (right!=null) { + sorted.next=right; + right=right.next; + } + } else if (right==null) { + while (left!=null) { + sorted.next=left; + left=left.next; + } + } + return sorted; + } + + // MAIN. Run some examples. The comments show what must be printed. + + public static void main(String[] args) { + writeNodes(sortNodes(makeNodes())); // [] + writeNodes(sortNodes(makeNodes(1))); // [1] + writeNodes(sortNodes(makeNodes(1, 2))); // [1, 2] + writeNodes(sortNodes(makeNodes(2, 1))); // [1, 2] + + writeNodes(sortNodes(makeNodes(1, 2, 3, 4, 5, 6, 7, 8, 9))); + // [1, 2, 3, 4, 5, 6, 7, 8, 9] + + writeNodes(sortNodes(makeNodes(9, 8, 7, 6, 5, 4, 3, 2, 1))); + // [1, 2, 3, 4, 5, 6, 7, 8, 9] + + writeNodes(sortNodes(makeNodes(3, 1, 4, 5, 9, 2, 6, 8, 7))); + // [1, 2, 3, 4, 5, 6, 7, 8, 9] + } +}
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