From 8df221cd1bfb51292066740698a00a7b782ac32d Mon Sep 17 00:00:00 2001
From: norangebit <git@norangeb.it>
Date: Mon, 11 Mar 2019 22:47:26 +0100
Subject: [PATCH] add peek to queue interface

- update travis file
- fix typo
---
 .travis.yml                                      | 10 ++++++++++
 .../algorithms/datastructures/queue/Queue.kt     |  1 +
 .../datastructures/queue/ResizingArrayQueue.kt   | 16 ++++++++++++----
 .../queue/ResizingArrayQueueTest.kt              | 11 +++++++++++
 .../stack/ResizingArrayStackTest.kt              |  4 ++--
 5 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 1b48652..92b9cbe 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,8 +1,18 @@
 language: java
+
 jdk:
   - oraclejdk8
+  - oraclejdk9
+  - openjdk10
+
+cache:
+  directories:
+    - ~/.gradle/caches/
+    - ~/.gradle/wrapper/
+
 before_install:
   - chmod +x gradlew
   - chmod +x gradle/wrapper/gradle-wrapper.jar
+
 script:
   - ./gradlew test build
diff --git a/src/main/kotlin/it/norangeb/algorithms/datastructures/queue/Queue.kt b/src/main/kotlin/it/norangeb/algorithms/datastructures/queue/Queue.kt
index 095ca0c..1c20de0 100644
--- a/src/main/kotlin/it/norangeb/algorithms/datastructures/queue/Queue.kt
+++ b/src/main/kotlin/it/norangeb/algorithms/datastructures/queue/Queue.kt
@@ -30,6 +30,7 @@ import arrow.core.Option
 interface Queue<T> {
     fun enqueue(elem: T)
     fun dequeue(): Option<T>
+    fun peek(): Option<T>
     fun isEmpty(): Boolean
     fun size(): Int
     fun clean()
diff --git a/src/main/kotlin/it/norangeb/algorithms/datastructures/queue/ResizingArrayQueue.kt b/src/main/kotlin/it/norangeb/algorithms/datastructures/queue/ResizingArrayQueue.kt
index 2cdc28a..6c24d29 100644
--- a/src/main/kotlin/it/norangeb/algorithms/datastructures/queue/ResizingArrayQueue.kt
+++ b/src/main/kotlin/it/norangeb/algorithms/datastructures/queue/ResizingArrayQueue.kt
@@ -51,10 +51,11 @@ class ResizingArrayQueue<T>(capacity: Int = DEFAULT_CAPACITY) : Queue<T> {
     }
 
     override fun dequeue(): Option<T> {
-        if (isEmpty())
-            return None
+        val elem = peek()
+
+        if (elem is None)
+            return elem
 
-        val elem = queue[head]
         queue[head] = null
         head = (head + 1) % queue.size
         size--
@@ -62,7 +63,14 @@ class ResizingArrayQueue<T>(capacity: Int = DEFAULT_CAPACITY) : Queue<T> {
         if (isOneQuarterFull())
             resizeArray(queue.size / RESIZE_FACTOR)
 
-        return elem.toOption()
+        return elem
+    }
+
+    override fun peek(): Option<T> {
+        if (isEmpty())
+            return None
+
+        return queue[head].toOption()
     }
 
     private fun resizeArray(capacity: Int) {
diff --git a/src/test/kotlin/it/norangeb/algorithms/datastructures/queue/ResizingArrayQueueTest.kt b/src/test/kotlin/it/norangeb/algorithms/datastructures/queue/ResizingArrayQueueTest.kt
index 1a2688a..be0bfdc 100644
--- a/src/test/kotlin/it/norangeb/algorithms/datastructures/queue/ResizingArrayQueueTest.kt
+++ b/src/test/kotlin/it/norangeb/algorithms/datastructures/queue/ResizingArrayQueueTest.kt
@@ -26,6 +26,7 @@
 package it.norangeb.algorithms.datastructures.queue
 
 import arrow.core.None
+import arrow.core.Some
 import arrow.core.getOrElse
 import org.amshove.kluent.`should be equal to`
 import org.junit.jupiter.api.Test
@@ -62,6 +63,16 @@ class ResizingArrayQueueTest {
         queue.size() `should be equal to` 0
     }
 
+    @Test
+    fun testPeek() {
+        val queue = ResizingArrayQueue<Int>()
+
+        (queue.peek() is None) `should be equal to` true
+        queue.enqueue(1)
+        (queue.peek() is Some) `should be equal to` true
+        queue.size() `should be equal to` 1
+    }
+
     @Test
     fun testIncreaseSize() {
         val queue = ResizingArrayQueue<Int>()
diff --git a/src/test/kotlin/it/norangeb/algorithms/datastructures/stack/ResizingArrayStackTest.kt b/src/test/kotlin/it/norangeb/algorithms/datastructures/stack/ResizingArrayStackTest.kt
index b4142e1..9ea7669 100644
--- a/src/test/kotlin/it/norangeb/algorithms/datastructures/stack/ResizingArrayStackTest.kt
+++ b/src/test/kotlin/it/norangeb/algorithms/datastructures/stack/ResizingArrayStackTest.kt
@@ -71,7 +71,7 @@ class ResizingArrayStackTest {
     }
 
     @Test
-    fun testIncrease() {
+    fun testIncreaseSize() {
         val stack = ResizingArrayStack<Int>()
 
         stack.push(1)
@@ -82,7 +82,7 @@ class ResizingArrayStackTest {
     }
 
     @Test
-    fun testDescrese() {
+    fun testDecreaseSize() {
         val stack = ResizingArrayStack<Int>()
 
         stack.push(1)