Added 26 solutions

2017-02-18 23:43:07 -06:00
parent 34e66564f9
commit 7034e7127c
45 changed files with 1458 additions and 89 deletions
@@ -0,0 +1,69 @@
+//     Author: Rodney Shaghoulian
+//     Github: github.com/rshaghoulian
+// HackerRank: hackerrank.com/rshaghoulian
+
+import java.util.Scanner;
+import java.util.Stack;
+
+public class Solution {
+    public static void main(String[] args) {
+        MyQueue<Integer> queue = new MyQueue<Integer>();
+
+        Scanner scan = new Scanner(System.in);
+        int n = scan.nextInt();
+
+        for (int i = 0; i < n; i++) {
+            int operation = scan.nextInt();
+            if (operation == 1) { // enqueue
+              queue.enqueue(scan.nextInt());
+            } else if (operation == 2) { // dequeue
+              queue.dequeue();
+            } else if (operation == 3) { // print/peek
+              System.out.println(queue.peek());
+            }
+        }
+        scan.close();
+    }
+    
+    public static class MyQueue<Integer> {
+        private Stack<Integer> stack1 = new Stack<>();
+        private Stack<Integer> stack2 = new Stack<>();
+        
+        public void enqueue(Integer num) {
+            stack1.push(num);
+        }
+        
+        public Integer dequeue() {
+            if (size() == 0) {
+                return null;
+            }
+            if (stack2.isEmpty()) {
+                shiftStacks();
+            }
+            return stack2.pop();
+        }
+        
+        public Integer peek() {
+            if (size() == 0) {
+                return null;
+            }
+            if (stack2.isEmpty()) {
+                shiftStacks();
+            }
+            return stack2.peek();
+        }
+        
+        /* Only shifts stacks if necessary */
+        private void shiftStacks() {
+            if (stack2.isEmpty()) { // shifting items while stack2 contains items would mess up our queue's ordering
+                while ( ! stack1.isEmpty()) {
+                    stack2.push(stack1.pop());
+                }
+            }
+        }
+        
+        public int size() {
+            return stack1.size() + stack2.size();
+        }
+    }
+}