insert into a cyclic sorted list

Author: xiaoningning

PuzzleCoding/src/InsertCyclicList.java

@@ -0,0 +1,73 @@
+/**
+ * Given a node from a cyclic linked list which has been sorted,
+ * write a function to insert a value into the list
+ * such that it remains a cyclic sorted list.
+ * The given node can be any single node in the list.
+ */
+public class InsertCyclicList {
+    private static class LinkedNode {
+        public int value;
+        public LinkedNode next;
+
+        public LinkedNode() {
+        }
+
+        public LinkedNode(int v) {
+            value = v;
+            next = null;
+        }
+
+        public String toString() {
+            return String.valueOf(value);
+        }
+
+        public LinkedNode clone() {
+            LinkedNode n = new LinkedNode(value);
+            n.next = next;
+            return n;
+        }
+    }  // end of linkednode class
+
+    public static void main(String[] args) {
+        LinkedNode n1 = new LinkedNode(1);
+        LinkedNode n2 = new LinkedNode(2);
+        LinkedNode n4 = new LinkedNode(4);
+        LinkedNode n6 = new LinkedNode(6);
+        n1.next = n2;
+        n2.next = n4;
+        n4.next = n6;
+        n6.next = n1;
+
+        int x = 5;
+        // list must be sorted.
+        insertCyclicList(n1, x);
+        LinkedNode p = n1;
+        do {
+            System.out.print(p.toString());
+            p = p.next;
+        } while (!p.equals(n1));
+
+    }
+
+    public static void insertCyclicList(LinkedNode head, int x) {
+        if (head == null) {
+            LinkedNode n = new LinkedNode(x);
+            n.next = n;
+            head = n;
+        }
+
+        LinkedNode p = head.clone();
+        LinkedNode prev;
+        do {
+            prev = p;
+            p = p.next;
+            if (x <= p.value && x >= prev.value) break;
+            // x is min or max of the list
+            if ((prev.value > p.value) && (x < p.value || x > prev.value)) break;
+        } while (!p.equals(head));
+
+        LinkedNode n = new LinkedNode(x);
+        prev.next = n;
+        n.next = p;
+    }
+}