# HG changeset patch
# User Eris Caffee <discordia@eldalin.com>
# Date 1432952012 18000
# Node ID b02533162b6ec2c848615f122df542281835b4aa
# Parent  a5052f77ba7e80371de3441d1dc8e29e8de73622
Linked list based Queue class.

diff -r a5052f77ba7e -r b02533162b6e algs4-c++/src/Queue.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/algs4-c++/src/Queue.cpp	Fri May 29 21:13:32 2015 -0500
@@ -0,0 +1,159 @@
+// g++ -D QUEUE_MAIN -std=c++0x Queue.cpp
+// g++ -D QUEUE_MAIN -std=c++11 Queue.cpp
+
+
+#include "Queue.hpp"
+
+#include <cassert>
+#include <cstddef>
+
+#include <iostream>
+
+template <typename T>
+Queue<T>::Queue( void ) :
+    N (0),
+    first (nullptr),
+    last (nullptr)
+    {
+    }
+    
+template <typename T>
+Queue<T>::~Queue( void ) {
+    assert( N == 0 );  // Catch the potential memory leak.
+    while ( first ) {
+        Node *next = first->next;
+        delete first;
+        first = next;
+        }
+    }
+
+template <typename T>
+void Queue<T>::enqueue( T &item ) {
+    Node * node = new Node();
+    node->item = item;
+    node->next = nullptr;
+
+    if ( last ) {
+        last->next = node;
+        last = node;
+        }
+    else {
+        last = first = node;
+        }
+
+    N++;
+    }
+
+template <typename T>
+T Queue<T>::dequeue( void ) {
+    assert( N > 0 );
+
+    T item = first->item;
+
+    Node *old = first;
+    first = first->next;
+    delete old;
+    N--;
+
+    if ( ! first )
+        last = nullptr;
+
+    return item;
+    }
+
+template <typename T>
+bool Queue<T>::is_empty( void ) {
+    return N == 0;
+    }
+
+template <typename T>
+size_t Queue<T>::size( void ) {
+    return N;
+    }
+
+template <typename T>
+typename Queue<T>::iterator Queue<T>::begin( void ) {
+    return Queue<T>::iterator( first );
+    }
+
+template <typename T>
+typename Queue<T>::iterator Queue<T>::end( void ) {
+    return Queue<T>::iterator( nullptr );
+    }
+
+
+////////////////////////////////////////////////////////////////////////////////
+
+template <typename T>
+Queue<T>::iterator::iterator( Node *c ) :
+    curr (c)
+    {
+    }
+
+template <typename T>
+typename Queue<T>::iterator & Queue<T>::iterator::operator++() {
+    if ( this->curr != nullptr ) {
+        this->curr = this->curr->next;
+        }
+    return *this;
+    }
+
+template <typename T>
+typename Queue<T>::iterator Queue<T>::iterator::operator++( int ) {
+    auto t = Queue<T>::iterator( *this );
+
+    if ( this->curr != nullptr ) {
+        this->curr = this->curr->next;
+        }
+    return t;
+    }
+
+template <typename T>
+T Queue<T>::iterator::operator*() {
+    return this->curr->item;
+    }
+
+template <typename T>
+bool Queue<T>::iterator::operator!=( typename Queue<T>::iterator other ) {
+    return this->curr != other.curr;
+    }
+
+
+////////////////////////////////////////////////////////////////////////////////
+
+#ifdef QUEUE_MAIN
+
+#include <iostream>
+
+int main ( int argc, char **argv ) {
+
+    Queue<long> queue;
+
+    long i;
+    while ( ! std::cin.eof() ) {
+        std::cin >> i;
+        if ( std::cin.good() ) 
+            if ( i >= 0 )
+                queue.enqueue(i);
+            else
+                queue.dequeue();
+        }
+
+    std::cout << "Queue has " << queue.size() << " entries." << std::endl;
+
+    for ( auto iter = queue.begin(); iter != queue.end(); ++iter ) {
+        std::cout << *iter << std::endl;
+        }
+
+    std::cout << "Dequeuing entries..." << std::endl;
+
+    while ( ! queue.is_empty() ) {
+        i = queue.dequeue();
+        std::cout << i << std::endl;
+        }
+
+    std::cout << "Queue has " << queue.size() << " entries." << std::endl;
+
+    }
+
+#endif
diff -r a5052f77ba7e -r b02533162b6e algs4-c++/src/Queue.hpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/algs4-c++/src/Queue.hpp	Fri May 29 21:13:32 2015 -0500
@@ -0,0 +1,66 @@
+#ifndef QUEUE_HPP
+#define QUEUE_HPP
+
+#include <cstddef>
+
+// Linked list based queue after Sedgewick and Wayne, Algorithms 4th ed, Algorithm 1.3
+
+template <typename T>
+class Queue {
+
+public:
+
+    ////////////////////////////////////
+    class Node {
+    public:
+        T item;
+        Node *next;
+        };
+
+
+    ////////////////////////////////////
+    class iterator;
+    friend class iterator;
+    class iterator {
+
+    public:
+
+        iterator( Node *c );
+
+        iterator& operator++();
+        iterator operator++(int);
+
+        T operator*();
+        bool operator!=( typename Queue<T>::iterator );
+
+    private:
+
+        Node *curr;
+        };
+
+    ////////////////////////////////////
+
+    Queue( void );
+    ~Queue( void );
+
+    void enqueue( T &item );
+    T dequeue( void );
+
+    bool is_empty( void );
+    size_t size( void );
+
+    iterator begin( void );
+    iterator end( void );
+
+private:
+
+    size_t N;
+    Node *first;
+    Node *last;
+
+    };
+
+
+
+#endif
+