Added sliding window

Readme.org

@@ -44,13 +44,13 @@ To run the tests:
 #+end_src
 
 * Plan
-** Arrays [2/6]
+** Arrays [3/6]
 - [X] Is Unique (CTCI: 1.1)
 - [X] Check permutation (CTCI: 1.2)
 - [ ] String Compression (CTCI: 1.6)
 - [ ] Rotate Matrix (CTCI: 1.7)
 - [ ] Zero Matrix (CTCI: 1.8)
-- [ ] Sliding Window ([[https://www.geeksforgeeks.org/window-sliding-technique/][GfG: Sliding Window Technique]])
+- [X] Sliding Window ([[https://www.geeksforgeeks.org/window-sliding-technique/][GfG: Sliding Window Technique]])
 ** Linked Lists [1/6]
 - [X] Remove Duplicates (CTCI: 2.1)
 - [ ] Return Kth to Last (CTCI: 2.2)
@@ -60,15 +60,15 @@ To run the tests:
 ** Stacks and Queues [0/2]
 - [ ] Stack Min (CTCI: 3.1)
 - [ ] Sort Stack (CTCI: 3.5)
-** Trees and Graphs [4/9]
+** Trees and Graphs [7/9]
 - [X] Implement binary tree object
   - Insert breadth first
 - [X] Recursive Pre-order traversal
 - [X] Recursive In-order traversal
 - [X] Recursive Post-order traversal
-- [ ] Non-Recursive Pre-order traversal
+- [X] Non-Recursive Pre-order traversal
-- [ ] Non-Recursive In-order traversal
+- [X] Non-Recursive In-order traversal
-- [ ] Non-Recursive Post-order traversal
+- [X] Non-Recursive Post-order traversal
 - [ ] Min Heap
 - [ ] Binary Search
 ** C/C++ [2/5]

libs/chapter1/chapter1.hpp

@@ -4,3 +4,5 @@
 
 bool IsUnique(const char* s, int len);
 bool CheckPermutation(const char* s1, const char* s2, size_t s1_len, size_t s2_len);
+int sliding_window_max_sum(int* array, int len, int k_len);
+int sliding_window_shortest_subarray(int* array,int len, int x);

libs/chapter1/meson.build

@@ -1,5 +1,6 @@
 
-chapter1_sources = ['is_unique.cpp', 'check_permutation.cpp']
+chapter1_sources = ['is_unique.cpp', 'check_permutation.cpp',
+                    'sliding_window.cpp']
 
 chapter1_lib = static_library('chapter1',
                               chapter1_sources)

libs/chapter1/sliding_window.cpp

@@ -0,0 +1,82 @@
+#include "chapter1.hpp"
+
+/**
+ *  \brief sliding_window_max_sum
+ *
+ *  Detailed description
+ *
+ *  \param array The input array
+ *  \param len The length of the input array
+ *  \param k_len The length of the subarray
+ *  \return return int The maximum found in the subarray
+ */
+int sliding_window_max_sum(int* array, int len, int k_len){
+  int current_max = 0;
+  int* window_beg = array;
+  int* window_end = (array + k_len);
+  int previous_beg = 0;
+  // initial sum
+  for (int i = 0; i < k_len; i++){
+    current_max += array[i];
+  }
+  previous_beg = *window_beg;
+  window_beg += 1;
+  window_end += 1;
+
+  // iterate window
+  int current_sum = current_max;
+  while(window_end != (array + len - 1)){
+    current_sum = current_sum - previous_beg + *window_end;
+    if (current_sum > current_max){
+      current_max = current_sum;
+    }
+    previous_beg = *window_beg;
+    window_beg += 1;
+    window_end += 1;
+  }
+
+  return current_max;
+}
+
+
+/**
+ *  \brief sliding_window_shortest_subarray
+ *
+ *  Find the shortest subarray that is greater than or equal to x.
+ *
+ *  \param array The intput array
+ *  \param len The length of the input array
+ *  \param x The threshold to compare to
+ *  \return return the length of the shortest subarray
+ */
+int sliding_window_shortest_subarray(int* array,int len, int x){
+
+  int* window_beg = &array[0];
+  int* window_end = &array[1];
+  int current_sum = array[0] + array[1];
+  int min_len = len;
+  int sub_array_len = len;
+
+
+  while(window_beg != (array + len - 1)){
+    if(current_sum < x){
+      window_end += 1;
+      current_sum += *window_end;
+    }
+    if (current_sum >= x){
+      sub_array_len = window_end - window_beg + 1;
+      if(sub_array_len < min_len){
+        min_len = sub_array_len;
+      }
+      current_sum -= *window_beg;
+      window_beg += 1;
+      if(window_beg > window_end){
+        window_end += 1;
+        current_sum += *window_end;
+      }
+    }
+
+  }
+
+  return min_len;
+}

libs/chapter12/reverse_string.cpp

@@ -9,7 +9,7 @@
 
 void reverse_str(char *str){
   size_t len = strlen(str);
-  char *tmp = reinterpret_cast<char*>(malloc(len));
+  char *tmp = reinterpret_cast<char*>(malloc(len + 1));
   strcpy(tmp, str);
   for(unsigned int offset = 0; offset < len; ++offset){
     str[offset] = tmp[len-offset-1];

libs/dope/bintree.hpp

@@ -1,6 +1,12 @@
 #pragma once
 
 #include <queue>
+#include <stack>
+
+typedef enum AlgoVariant_E{
+  Recursive,
+  Iter,
+}AlgoVariant;
 
 template <class T>
 class DopeBinTreeNode{
@@ -23,6 +29,9 @@ class DopeBinTree{
   T* RecPreOrderTraversal(DopeBinTreeNode<T>* node, T* out);
   T* RecInOrderTraversal(DopeBinTreeNode<T>* node, T* out);
   T* RecPostOrderTraversal(DopeBinTreeNode<T>* node, T* out);
+  void IterPreOrderTraversal(DopeBinTreeNode<T>* node, T* out);
+  void IterInOrderTraversal(DopeBinTreeNode<T>* node, T* out);
+  void IterPostOrderTraversal(DopeBinTreeNode<T>* node, T* out);
 public:
   DopeBinTree(T data);
   DopeBinTree();
@@ -30,9 +39,9 @@ public:
   void insert(T data);
   bool isEmpty();
   DopeBinTreeNode<T>* getRoot(){return root;}
-  void RecPreOrderTraversalArray(T* array);
+  void PreOrderTraversal2Array(T* array, AlgoVariant variant);
-  void RecInOrderTraversalArray(T* array);
+  void InOrderTraversal2Array(T* array, AlgoVariant variant);
-  void RecPostOrderTraversalArray(T* array);
+  void PostOrderTraversal2Array(T* array, AlgoVariant variant);
 };
 
 // Implementations ___________________________________________________
@@ -147,26 +156,145 @@ T* DopeBinTree<T>::RecPostOrderTraversal(DopeBinTreeNode<T>* node, T* out){
 }
 
 template <class T>
-void DopeBinTree<T>::RecPreOrderTraversalArray(T* array){
+void DopeBinTree<T>::IterPreOrderTraversal(DopeBinTreeNode<T>* node, T* out){
+  std::stack<DopeBinTreeNode<T>*> s = {};
+  s.push(node);
+
+  while(s.empty() == false){
+    node = s.top();
+    s.pop();
+    *out = node->GetData();
+    out++;
+    if(node->GetRight()){
+      s.push(node->GetRight());
+    }
+    if(node->GetLeft()){
+      s.push(node->GetLeft());
+    }
+  }
+}
+
+template <class T>
+void DopeBinTree<T>::IterInOrderTraversal(DopeBinTreeNode<T>* node, T* out){
+  std::stack<DopeBinTreeNode<T>*> s = {};
+
+  while (!s.empty() || node){
+    while(node != nullptr){
+      s.push(node);
+      node = node->GetLeft();
+    }
+    node = s.top();
+    s.pop();
+    *out = node->GetData();
+    out++;
+    node = node->GetRight();
+  }
+
+}
+
+template <class T>
+void DopeBinTree<T>::IterPostOrderTraversal(DopeBinTreeNode<T>* node, T* out){
+  std::stack<DopeBinTreeNode<T>*> s_tmp = {};
+  std::stack<DopeBinTreeNode<T>*> s_fin = {};
+
+  s_tmp.push(node);
+  while(!s_tmp.empty()){
+    node = s_tmp.top();
+    s_tmp.pop();
+    s_fin.push(node);
+
+    if(node->GetLeft()){
+      s_tmp.push(node->GetLeft());
+    }
+    if(node->GetRight()){
+      s_tmp.push(node->GetRight());
+    }
+  }
+
+  while(!s_fin.empty()){
+    node = s_fin.top();
+    s_fin.pop();
+    *out = node->GetData();
+    out++;
+  }
+}
+
+/**
+ *  \brief PreOrderTraversal2Array
+ *
+ *  Binary tree traversal that visits the root node, then the left
+ *  sub-tree, and then the right-subtree.
+ *
+ *  \param The output array
+ *  \param The algorithm variant
+ *  \return return type
+ */
+template <class T>
+void DopeBinTree<T>::PreOrderTraversal2Array(T* array, AlgoVariant variant){
   int index = 0;
   DopeBinTreeNode<T>* node = root;
-
+  switch(variant){
+  case AlgoVariant::Recursive:
     RecPreOrderTraversal(node, &array[index]);
-
+    return;
+  case AlgoVariant::Iter:
+    IterPreOrderTraversal(node, &array[index]);
+    return;
+  default:
+    return;
+  }
 }
 
+/**
+ *  \brief InOrderTraversal2Array
+ *
+ *  Binary tree traversal that traverses the left sub-tree, then
+ *  visits the root node, then the right-subtree.
+ *
+ *  \param The output array
+ *  \param The algorithm variant
+ *  \return return type
+ */
 template <class T>
-void DopeBinTree<T>::RecInOrderTraversalArray(T* array){
+void DopeBinTree<T>::InOrderTraversal2Array(T* array, AlgoVariant variant){
   int index = 0;
   DopeBinTreeNode<T>* node = root;
-
+  switch(variant){
+  case AlgoVariant::Recursive:
     RecInOrderTraversal(node, &array[index]);
+    return;
+  case AlgoVariant::Iter:
+    IterInOrderTraversal(node, &array[index]);
+    return;
+  default:
+    return;
+  }
 }
 
+
+/**
+ *  \brief PostOrderTraversal2Array
+ *
+ *  Binary tree traversal that visits left-subtree, right subtree, and
+ *  then the root node.
+ *
+ *  \param The output array
+ *  \param The algorithm variant
+ *  \return return type
+ */
 template <class T>
-void DopeBinTree<T>::RecPostOrderTraversalArray(T* array){
+void DopeBinTree<T>::PostOrderTraversal2Array(T* array, AlgoVariant variant){
   int index = 0;
   DopeBinTreeNode<T>* node = root;
 
+  switch(variant){
+  case AlgoVariant::Recursive:
     RecPostOrderTraversal(node, &array[index]);
+    return;
+  case AlgoVariant::Iter:
+    IterPostOrderTraversal(node, &array[index]);
+    return;
+  default:
+    return;
+  }
 }

tests/test.cpp

@@ -32,6 +32,20 @@ TEST(ChapterOne, CheckPermutations){
 
 }
 
+TEST(ChapterOne, SubArraySum){
+  // Not actually in CTCI but is related to arrays
+
+  // Prompt: Given an array, find the sum of all subarrays of length K
+  // (fixed sliding window)
+  int a1[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+  CHECK_EQUAL(27, sliding_window_max_sum(a1, 11, 3));
+
+  // Prompt: Find the shortest subarray with a sum greater than or
+  // equal to X (dynamic sliding window)
+  int a2[] = {0, 1, 2, 3, 4, 5, 6, 7, 8};
+  CHECK_EQUAL(1, sliding_window_shortest_subarray(a2, 9, 7));
+}
+
 // Chapter 2: Linked Lists ___________________________________________
 
 TEST_GROUP(ChapterTwo){};
@@ -136,7 +150,7 @@ TEST(ChapterFour, TreeTraversal){
 
   int array[10] = {};
 
-  btree.RecPreOrderTraversalArray(array);
+  btree.PreOrderTraversal2Array(array, AlgoVariant::Recursive);
   CHECK_EQUAL(1, array[0]);
   CHECK_EQUAL(2, array[1]);
   CHECK_EQUAL(4, array[2]);
@@ -147,7 +161,7 @@ TEST(ChapterFour, TreeTraversal){
 
   std::fill(array, array+10, 0);
 
-  btree.RecInOrderTraversalArray(array);
+  btree.InOrderTraversal2Array(array, AlgoVariant::Recursive);
   CHECK_EQUAL(4, array[0]);
   CHECK_EQUAL(2, array[1]);
   CHECK_EQUAL(5, array[2]);
@@ -158,7 +172,40 @@ TEST(ChapterFour, TreeTraversal){
 
   std::fill(array, array+10, 0);
 
-  btree.RecPostOrderTraversalArray(array);
+  btree.PostOrderTraversal2Array(array, AlgoVariant::Recursive);
+  CHECK_EQUAL(4, array[0]);
+  CHECK_EQUAL(5, array[1]);
+  CHECK_EQUAL(2, array[2]);
+  CHECK_EQUAL(6, array[3]);
+  CHECK_EQUAL(7, array[4]);
+  CHECK_EQUAL(3, array[5]);
+  CHECK_EQUAL(1, array[6]);
+
+  std::fill(array, array+10, 0);
+
+  btree.PreOrderTraversal2Array(array, AlgoVariant::Iter);
+  CHECK_EQUAL(1, array[0]);
+  CHECK_EQUAL(2, array[1]);
+  CHECK_EQUAL(4, array[2]);
+  CHECK_EQUAL(5, array[3]);
+  CHECK_EQUAL(3, array[4]);
+  CHECK_EQUAL(6, array[5]);
+  CHECK_EQUAL(7, array[6]);
+
+  std::fill(array, array+10, 0);
+
+  btree.InOrderTraversal2Array(array, AlgoVariant::Iter);
+  CHECK_EQUAL(4, array[0]);
+  CHECK_EQUAL(2, array[1]);
+  CHECK_EQUAL(5, array[2]);
+  CHECK_EQUAL(1, array[3]);
+  CHECK_EQUAL(6, array[4]);
+  CHECK_EQUAL(3, array[5]);
+  CHECK_EQUAL(7, array[6]);
+
+  std::fill(array, array+10, 0);
+
+  btree.PostOrderTraversal2Array(array, AlgoVariant::Iter);
   CHECK_EQUAL(4, array[0]);
   CHECK_EQUAL(5, array[1]);
   CHECK_EQUAL(2, array[2]);