# HG changeset patch
# User Eris Caffee <discordia@eldalin.com>
# Date 1433960486 18000
# Node ID 846aeab17939fa311192aa4c027b717ae22e3d09
# Parent  8af1a61be7c11e2fc719beda49221d5038fc174b
Added Steque (exercise 1.3.32)

diff -r 8af1a61be7c1 -r 846aeab17939 algs4-c++/src/Steque.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/algs4-c++/src/Steque.cpp	Wed Jun 10 13:21:26 2015 -0500
@@ -0,0 +1,178 @@
+// g++ -D STEQUE_MAIN -std=c++0x Steque.cpp
+// g++ -D STEQUE_MAIN -std=c++11 Steque.cpp
+
+
+#include "Steque.hpp"
+
+#include <cassert>
+#include <cstddef>
+
+#include <iostream>
+
+template <typename T>
+Steque<T>::Steque( void ) :
+    N (0),
+    list (nullptr)
+    {
+    }
+    
+template <typename T>
+Steque<T>::~Steque( void ) {
+    assert( N == 0 );  // Catch the potential memory leak.
+    while ( list ) {
+        Node * next = list->next;
+        delete list;
+        list = next;
+        }
+    }
+
+template <typename T>
+void Steque<T>::push( T &item ) {
+    Node * node = new Node();
+    node->item = item;
+    node->next = list;
+    list = node;
+    N++;
+    }
+
+template <typename T>
+T Steque<T>::pop( void ) {
+    assert( N > 0 );
+
+    T item = list->item;
+
+    Node *old = list;
+    list = list->next;
+    delete old;
+    N--;
+
+    return item;
+    }
+
+template <typename T>
+void Steque<T>::enqueue( T &item ) {
+    Node *curr = list;
+
+    Node *node = new Node();
+    node->item = item;
+    node->next = nullptr;
+
+    if ( ! curr ) {
+        list = node;
+        N++;
+        return;
+        }
+
+    while ( curr->next ) {
+        curr = curr->next;
+        }
+
+    curr->next = node;
+    N++;
+
+    return;
+    }
+
+template <typename T>
+bool Steque<T>::is_empty( void ) {
+    return N == 0;
+    }
+
+template <typename T>
+size_t Steque<T>::size( void ) {
+    return N;
+    }
+
+template <typename T>
+typename Steque<T>::iterator Steque<T>::begin( void ) {
+    return Steque<T>::iterator( list );
+    }
+
+template <typename T>
+typename Steque<T>::iterator Steque<T>::end( void ) {
+    return Steque<T>::iterator( nullptr );
+    }
+
+
+////////////////////////////////////////////////////////////////////////////////
+
+template <typename T>
+Steque<T>::iterator::iterator( Node *c ) :
+    curr (c)
+    {
+    }
+
+template <typename T>
+typename Steque<T>::iterator & Steque<T>::iterator::operator++() {
+    if ( this->curr != nullptr ) {
+        this->curr = this->curr->next;
+        }
+    return *this;
+    }
+
+template <typename T>
+typename Steque<T>::iterator Steque<T>::iterator::operator++( int ) {
+    auto t = Steque<T>::iterator( *this );
+
+    if ( this->curr != nullptr ) {
+        this->curr = this->curr->next;
+        }
+    return t;
+    }
+
+template <typename T>
+T Steque<T>::iterator::operator*() {
+    return this->curr->item;
+    }
+
+template <typename T>
+bool Steque<T>::iterator::operator!=( typename Steque<T>::iterator other ) {
+    return this->curr != other.curr;
+    }
+
+////////////////////////////////////////////////////////////////////////////////
+
+
+
+#ifdef STEQUE_MAIN
+
+#include <iostream>
+
+int main ( int argc, char **argv ) {
+
+    Steque<long> steque;
+    bool push_it = true;
+
+    long i;
+    while ( ! std::cin.eof() ) {
+        std::cin >> i;
+        if ( std::cin.good() )  {
+            if ( push_it ) {
+                steque.push( i );
+                push_it = false;
+                }
+            else {
+                steque.enqueue( i );
+                push_it = true;
+                }
+            }
+        }
+
+    std::cout << "Steque has " << steque.size() << " entries." << std::endl;
+
+    for ( auto iter = steque.begin(); iter != steque.end(); ++iter ) {
+        std::cout << *iter << std::endl;
+        }
+
+    std::cout << "Popping entries..." << std::endl;
+
+    while ( ! steque.is_empty() ) {
+        i = steque.pop();
+        std::cout << i << std::endl;
+        }
+
+    std::cout << "Steque has " << steque.size() << " entries." << std::endl;
+
+    }
+
+#endif
diff -r 8af1a61be7c1 -r 846aeab17939 algs4-c++/src/Steque.hpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/algs4-c++/src/Steque.hpp	Wed Jun 10 13:21:26 2015 -0500
@@ -0,0 +1,68 @@
+#ifndef STEQUE_HPP
+#define STEQUE_HPP
+
+#include <cstddef>
+
+// Linked list based steque after Sedgewick and Wayne, Algorithms 4th ed, Algorithm 1.2
+
+template <typename T>
+class Steque {
+
+private:
+
+    ////////////////////////////////////
+    class Node {
+    public:
+        T item;
+        Node *next;
+        };
+
+
+public:
+
+    ////////////////////////////////////
+    class iterator;
+    friend class iterator;
+    class iterator {
+
+    public:
+
+        iterator( Node *c );
+
+        iterator& operator++();
+        iterator operator++(int);
+
+        T operator*();
+        bool operator!=( typename Steque<T>::iterator );
+
+    private:
+
+        Node *curr;
+        };
+
+    ////////////////////////////////////
+
+    Steque( void );
+    ~Steque( void );
+
+    void push( T &item );
+    T pop( void );
+    void enqueue( T &item );
+
+    bool is_empty( void );
+    size_t size( void );
+
+    iterator begin( void );
+    iterator end( void );
+
+private:
+
+    size_t N;
+    Node *list;
+
+    };
+
+
+
+#endif
+