Added 27 solutions

30 Days of Code/Day 12 - Inheritance/Solution.java

@@ -53,20 +53,15 @@ public char calculate() {
 
         if  (average >= 90) {
             return 'O';
-        }
-        else if (average >= 80) {
+        } else if (average >= 80) {
             return 'E';
-        }
-        else if (average >= 70) {
+        } else if (average >= 70) {
             return 'A';
-        }
-        else if (average >= 55) {
+        } else if (average >= 55) {
             return 'P';
-        }
-        else if (average >= 40) {
+        } else if (average >= 40) {
             return 'D';
-        }
-        else {
+        } else {
             return 'T';
         }
     }

30 Days of Code/Day 14 - Scope/Solution.java

@@ -16,16 +16,12 @@ class Difference {
         this.elements = elements;
     }
 
-    // O(n) runtime. O(1) space
+    //          Runtime: O(n)
+    // Space Complexity: O(1)
     void computeDifference() {
-        maximumDifference = 0;
-        int min = elements[0];
-        int max = elements[0];
-        for (int num : elements) {
-            min = Math.min(min, num);
-            max = Math.max(max, num);
-        }
-        maximumDifference = max - min;
+        int max = Arrays.stream(elements).max().getAsInt();
+        int min = Arrays.stream(elements).min().getAsInt();     
+        maximumDifference = max - min ;
     }
 } // End of Difference class
 

30 Days of Code/Day 16 - Exceptions - String to Integer/Solution.java

@@ -8,12 +8,12 @@ public class Solution {
     public static void main(String[] args) {
         Scanner scan = new Scanner(System.in);
         String str = scan.next();
+        scan.close();
         try {
             int num = Integer.parseInt(str);
             System.out.println(num);
         } catch (NumberFormatException e) {
             System.out.println("Bad String");
         }
-        scan.close();
     }
 }

30 Days of Code/Day 23 - BST Level-Order Traversal/Solution.java

@@ -0,0 +1,61 @@
+//     Author: Rodney Shaghoulian
+//     Github: github.com/rshaghoulian
+// HackerRank: hackerrank.com/rshaghoulian
+
+import java.io.*;
+import java.util.*;
+
+class Node {
+    Node left,right;
+    int data;
+    Node(int data) {
+        this.data = data;
+        left = right = null;
+    }
+}
+
+class Solution {
+    static void levelOrder(Node root){
+        Queue<Node> queue = new LinkedList<>();
+        if (root != null) {
+            queue.add(root);
+        }
+        while ( ! queue.isEmpty()) {
+            Node n = queue.remove();
+            System.out.print(n.data + " ");
+            if (n.left != null) {
+                queue.add(n.left);
+            }
+            if (n.right != null) {
+                queue.add(n.right);
+            }
+        }
+    }
+
+    public static Node insert(Node root,int data){
+        if (root == null) {
+            return new Node(data);
+        } else {
+            Node cur;
+            if (data <= root.data) {
+                cur = insert(root.left, data);
+                root.left = cur;
+            }
+            else {
+                cur = insert(root.right, data);
+                root.right = cur;
+            }
+            return root;
+        }
+    }
+    public static void main(String args[]) {
+        Scanner sc = new Scanner(System.in);
+        int T = sc.nextInt();
+        Node root = null;
+        while (T-- > 0) {
+            int data = sc.nextInt();
+            root = insert(root, data);
+        }
+        levelOrder(root);
+    }   
+}

30 Days of Code/Day 24 - More Linked Lists/Solution.java

@@ -0,0 +1,67 @@
+//     Author: Rodney Shaghoulian
+//     Github: github.com/rshaghoulian
+// HackerRank: hackerrank.com/rshaghoulian
+
+import java.io.*;
+import java.util.*;
+
+class Node {
+    int data;
+    Node next;
+    Node(int d) {
+        data = d;
+        next = null;
+    }
+}
+
+class Solution {
+    public static Node removeDuplicates(Node head) {
+        if (head == null) {
+            return null;
+        }
+        Node n = head;
+        while (n.next != null) {
+            if (n.data == n.next.data) {
+                n.next = n.next.next;
+            } else {
+                n = n.next;
+            }
+        }
+        return head;
+    }
+
+    public static Node insert(Node head,int data) {
+        Node p = new Node(data);
+        if (head == null)
+            head = p;
+        else if (head.next == null)
+            head.next = p;
+        else {
+            Node start = head;
+            while (start.next != null)
+                start = start.next;
+            start.next = p;
+        }
+        return head;
+    }
+
+    public static void display(Node head) {
+        Node start = head;
+        while (start != null) {
+            System.out.print(start.data + " ");
+            start = start.next;
+        }
+    }
+
+    public static void main(String args[]) {
+        Scanner sc = new Scanner(System.in);
+        Node head = null;
+        int T = sc.nextInt();
+        while (T-- > 0) {
+            int ele = sc.nextInt();
+            head = insert(head, ele);
+        }
+        head = removeDuplicates(head);
+        display(head);
+   }
+}

30 Days of Code/Day 25 - Running Time and Complexity/Solution.java

@@ -0,0 +1,31 @@
+//     Author: Rodney Shaghoulian
+//     Github: github.com/rshaghoulian
+// HackerRank: hackerrank.com/rshaghoulian
+
+import java.util.Scanner;
+
+public class Solution {
+
+    public static void main(String[] args) {
+        Scanner scan = new Scanner(System.in);
+        int p = scan.nextInt();
+        for (int a0 = 0; a0 < p; a0++) {
+            int n = scan.nextInt();
+            System.out.println(isPrime(n) ? "Prime" : "Not prime");
+        }
+        scan.close();
+    }
+
+    public static boolean isPrime (int n) {
+        if (n < 2) {
+            return false;
+        }
+        int sqrt = (int) Math.sqrt(n);
+        for (int i = 2; i <= sqrt; i++) {
+            if (n % i == 0) {
+                return false;
+            }
+        }
+        return true;
+    }
+}

30 Days of Code/Day 26 - Nested Logic/Solution.java

@@ -0,0 +1,36 @@
+//     Author: Rodney Shaghoulian
+//     Github: github.com/rshaghoulian
+// HackerRank: hackerrank.com/rshaghoulian
+
+import java.util.Scanner;
+import java.time.LocalDate;
+
+public class Solution {
+    public static void main(String[] args) {
+        /* Read and save input as LocalDates */
+        Scanner scan = new Scanner(System.in);
+        LocalDate returnDate = readDate(scan);
+        LocalDate expectDate = readDate(scan);
+        scan.close();
+
+        /* Calculate fine */
+        int fine;
+        if (returnDate.isEqual(expectDate) || returnDate.isBefore(expectDate)) {
+            fine = 0;
+        } else if (returnDate.getMonth() == expectDate.getMonth() && returnDate.getYear() == expectDate.getYear()) {
+            fine = 15 * (returnDate.getDayOfMonth() - expectDate.getDayOfMonth());
+        } else if (returnDate.getYear() == expectDate.getYear()) {
+            fine = 500 * (returnDate.getMonthValue() - expectDate.getMonthValue());
+        } else {
+            fine = 10000;
+        }
+        System.out.println(fine);
+    }
+
+    private static LocalDate readDate(Scanner scan) {
+        int day   = scan.nextInt();
+        int month = scan.nextInt();
+        int year  = scan.nextInt();
+        return LocalDate.of(year, month, day);
+    }
+}

30 Days of Code/Day 27 - Testing/Solution.java

@@ -0,0 +1,24 @@
+//     Author: Rodney Shaghoulian
+//     Github: github.com/rshaghoulian
+// HackerRank: hackerrank.com/rshaghoulian
+
+public class Solution {
+    public static void main(String[] args) {
+        System.out.println(5);
+
+        System.out.println("4 3");
+        System.out.println("-1 0 1 2");
+
+        System.out.println("3 1");
+        System.out.println("-1 0 1");
+
+        System.out.println("5 4");
+        System.out.println("-1 0 1 2 3");
+
+        System.out.println("6 1");
+        System.out.println("-1 0 1 2 3 4");
+
+        System.out.println("7 6");
+        System.out.println("-1 0 1 2 3 4 5");
+    }
+}