Merging from origin, again

Author: jiegillet

.editorconfig

@@ -70,6 +70,11 @@ indent_size = 4
 indent_style = space
 indent_size = 2
 
+# Matlab
+[*.m]
+indent_style = space
+indent_size = 4
+
 # Markdown
 [*.md]
 indent_style = space
@@ -85,6 +90,11 @@ indent_size = 2
 indent_style = space
 indent_size = 4
 
+# Racket
+[*.rkt]
+indent_style = space
+indent_size = 2
+
 # Rust
 [*.rs]
 indent_style = space

CONTRIBUTORS.md

@@ -13,3 +13,4 @@ Chinmaya Mahesh
 Unlambder
 Kjetil Johannessen
 CDsigma
+DominikRafacz

chapters/FFT/cooley_tukey.md

@@ -58,11 +58,11 @@ Truth be told, I didn't understand it fully until I discretized real and frequen
 
 In principle, the Discrete Fourier Transform (DFT) is simply the Fourier transform with summations instead of integrals:
 
-$$X_k = \sum_{n=0}^{N-1} x_n \cdot e^{-2 \pi k n / N}$$
+$$X_k = \sum_{n=0}^{N-1} x_n \cdot e^{-2 \pi i k n / N}$$
 
 and
 
-$$x_n = \frac{1}{N} \sum_{k=0}^{N-1} X_k \cdot e^{2 \pi k n / N}$$
+$$x_n = \frac{1}{N} \sum_{k=0}^{N-1} X_k \cdot e^{2 \pi i k n / N}$$
 
 Where $$X_n$$ and $$x_n$$ are sequences of $$N$$ numbers in frequency and real space, respectively.
 In principle, this is no easier to understand than the previous case!
@@ -72,7 +72,7 @@ For some reason, though, putting code to this transformation really helped me fi
 {% sample lang="jl" %}
 [import:2-11, lang:"julia"](code/julia/fft.jl)
 {% sample lang="c" %}
-[import:7-19, lang:"c_cpp"](code/c/fft.c)
+[import:8-19, lang:"c_cpp"](code/c/fft.c)
 {% sample lang="cpp" %}
 [import:2-11, lang:"julia"](code/julia/fft.jl)
 {% sample lang="hs" %}
@@ -117,7 +117,7 @@ In the end, the code looks like:
 {% sample lang="jl" %}
 [import:14-31, lang:"julia"](code/julia/fft.jl)
 {% sample lang="c" %}
-[import:21-40, lang:"c_cpp"](code/c/fft.c)
+[import:20-39, lang:"c_cpp"](code/c/fft.c)
 {% sample lang="cpp" %}
 [import:27-57, lang:"c_cpp"](code/c++/fft.cpp)
 {% sample lang="hs" %}
@@ -138,12 +138,12 @@ Butterfly Diagrams show where each element in the array goes before, during, and
 As mentioned, the FFT must perform a DFT.
 This means that even though we need to be careful about how we add elements together, we are still ultimately performing the following operation:
 
-$$X_k = \sum_{n=0}^{N-1} x_n \cdot e^{-2 \pi k n / N}$$
+$$X_k = \sum_{n=0}^{N-1} x_n \cdot e^{-2 \pi i k n / N}$$
 
 However, after shuffling the initial array (by bit reversing or recursive subdivision), we perform the matrix multiplication of the $$e^{-2 \pi k n / N}$$ terms in pieces.
 Basically, we split the array into a series of omega values:
 
-$$\omega_N^k = e^{-2 \pi k / N}$$
+$$\omega_N^k = e^{-2 \pi i k / N}$$
 
 And at each step, we use the appropriate term.
 For example, imagine we need to perform an FFT of an array of only 2 elements.

chapters/differential_equations.md

@@ -0,0 +1,35 @@
+//submitted by DominikRafacz
+import java.util.Random;
+
+public class MonteCarlo {
+
+    public static void main(String[] args) {
+        monteCarlo(10_000_000);
+    }
+
+    //function to check whether point (x,y) is in unit circle
+    private static boolean inCircle(double x, double y) {
+        return x * x + y * y < 1;
+    }
+
+    //function to calculate estimation of pi
+    public static void monteCarlo(int samples) {
+        int piCount = 0;
+
+        Random random = new Random();
+
+        for (int i = 0; i < samples; i++) {
+            double x = random.nextDouble();
+            double y = random.nextDouble();
+            if (inCircle(x, y)) {
+                piCount++;
+            }
+        }
+
+        double estimation = 4.0 * piCount / samples;
+
+        System.out.println("Estimated pi value: " + estimation);
+        System.out.printf("Percent error: %.4f%%",  
+                          100 * (Math.PI - estimation) / Math.PI);
+    }
+}

chapters/monte_carlo/code/java/MonteCarlo.java

@@ -53,6 +53,8 @@ each point is tested to see whether it's in the circle or not:
 [import:2-5, lang:"d"](code/d/monte_carlo.d)
 {% sample lang="go" %}
 [import:12-14, lang:"golang"](code/go/monteCarlo.go)
+{% sample lang="java" %}
+[import:11-13, lang:"java"](code/java/MonteCarlo.java)
 {% endmethod %}
 
 If it's in the circle, we increase an internal count by one, and in the end,
@@ -108,6 +110,9 @@ Feel free to submit your version via pull request, and thanks for reading!
 {%sample lang="go" %}
 ### Go
 [import, lang:"golang"](code/go/monteCarlo.go)
+{% sample lang="java" %}
+### Java
+[import, lang:"java"](code/java/MonteCarlo.java)
 {% endmethod %}
 
 

chapters/monte_carlo/monte_carlo.md

@@ -8,7 +8,7 @@ imagine you have an array of $$n$$ elements that you want sorted.
 One way to do it is to shuffle the array at random and hope that all the elements will be magically in order after shuffling.
 If they are not in order, just shuffle everything again.
 And then again. And again.
-In the best case, this algorithm runs with a complexity of $$\Omega(1)$$, and in the worst, $$\mathcal{O}(\infty)$$.
+In the best case, this algorithm runs with a complexity of $$\Omega(n)$$, and in the worst, $$\mathcal{O}(\infty)$$.
 
 In code, it looks something like this:
 
@@ -18,9 +18,9 @@ In code, it looks something like this:
 {% sample lang="cs" %}
 [import:9-15, lang:"csharp"](code/cs/BogoSort.cs)
 {% sample lang="clj" %}
-[import:2-10, lang:"clojure"](code/clojure/bogo.clj)
+[import:2-11, lang:"clojure"](code/clojure/bogo.clj)
 {% sample lang="c" %}
-[import:4-27, lang:"c_cpp"](code/c/bogo_sort.c)
+[import:4-29, lang:"c_cpp"](code/c/bogo_sort.c)
 {% sample lang="java" %}
 [import:2-17, lang:"java"](code/java/bogo.java)
 {% sample lang="js" %}

chapters/sorting_searching/bogo/bogo_sort.md

@@ -13,7 +13,7 @@ This means that we need to go through the vector $$\mathcal{O}(n^2)$$ times with
 {% sample lang="cs" %}
 [import:9-27, lang:"csharp"](code/cs/BubbleSort.cs)
 {% sample lang="c" %}
-[import:3-21, lang:"c_cpp"](code/c/bubble_sort.c)
+[import:4-22, lang:"c_cpp"](code/c/bubble_sort.c)
 {% sample lang="java" %}
 [import:2-12, lang:"java"](code/java/bubble.java)
 {% sample lang="js" %}

chapters/sorting_searching/bubble/bubble_sort.md

@@ -1,9 +1,9 @@
 class Node:
-
     def __init__(self):
         self.data = None
         self.children = []
 
+
 def create_tree(node, num_row, num_child):
     node.data = num_row
 
@@ -14,12 +14,37 @@ def create_tree(node, num_row, num_child):
 
     return node
 
+
 def DFS_recursive(node):
-    if len(node.children) > 0:
+    if node.data != None:
+        print(node.data)
+
+    for child in node.children:
+        DFS_recursive(child)
+
+
+def DFS_recursive_postorder(node):
+    for child in node.children:
+        DFS_recursive(child)
+
+    if node.data != None:
         print(node.data)
 
-        for child in node.children:
-            DFS_recursive(child)
+
+# This assumes only 2 children, but accounts for other possibilities
+def DFS_recursive_inorder_btree(node):
+    if (len(node.children) == 2):
+        DFS_recursive_inorder_btree(node.children[1])
+        print(node.data)
+        DFS_recursive_inorder_btree(node.children[2])
+    elif (len(node.children) == 1):
+        DFS_recursive_inorder_btree(node.children[1])
+        print(node.data)
+    elif (len(node.children) == 0):
+        print(node.data)
+    else:
+        print("Not a binary tree!")
+
 
 def DFS_stack(node):
     stack = []
@@ -34,6 +59,7 @@ def DFS_stack(node):
         for child in temp.children:
             stack.append(child)
 
+
 def BFS_queue(node):
     queue = []
     queue.append(node)
@@ -47,6 +73,7 @@ def BFS_queue(node):
         for child in temp.children:
             queue.append(child)
 
+
 def main():
     tree = create_tree(Node(), 3, 3)
 
@@ -59,5 +86,7 @@ def main():
     print("Queue:")
     BFS_queue(tree)
 
-main()
+
+if __name__ == '__main__':
+    main()
 

chapters/tree_traversal/code/python/Tree_example.py

@@ -17,7 +17,7 @@ Trees are naturally recursive data structures, and because of this, we cannot ac
 This has not been implemented in your chosen language, so here is the Julia code
 [import:3-7, lang:"julia"](code/julia/Tree.jl)
 {% sample lang="py" %}
-[import:1-5, lang:"python"](code/python/Tree_example.py)
+[import:1-4, lang:"python"](code/python/Tree_example.py)
 {% sample lang="scratch" %}
 This has not been implemented in your chosen language, so here is the Julia code
 [import:3-7, lang:"julia"](code/julia/Tree.jl)
@@ -43,7 +43,7 @@ Because of this, the most straightforward way to traverse the tree might be recu
 {% sample lang="js" %}
 [import:12-15, lang:"javascript"](code/javascript/tree.js)
 {% sample lang="py" %}
-[import:7-15, lang:"python"](code/python/Tree_example.py)
+[import:18-23, lang:"python"](code/python/Tree_example.py)
 {% sample lang="scratch" %}
 This has not been implemented in your chosen language, so here is the Julia code
 [import:9-16, lang:"julia"](code/julia/Tree.jl)
@@ -79,8 +79,7 @@ This has not been implemented in your chosen language, so here is the Julia code
 {% sample lang="js" %}
 [import:17-20, lang:"javascript"](code/javascript/tree.js)
 {% sample lang="py" %}
-This has not been implemented in your chosen language, so here is the Julia code
-[import:18-26, lang:"julia"](code/julia/Tree.jl)
+[import:26-31, lang:"python"](code/python/Tree_example.py)
 {% sample lang="scratch" %}
 This has not been implemented in your chosen language, so here is the Julia code
 [import:18-26, lang:"julia"](code/julia/Tree.jl)
@@ -112,8 +111,7 @@ This has not been implemented in your chosen language, so here is the Julia code
 {% sample lang="js" %}
 [import:22-34, lang:"javascript"](code/javascript/tree.js)
 {% sample lang="py" %}
-This has not been implemented in your chosen language, so here is the Julia code
-[import:28-43, lang:"julia"](code/julia/Tree.jl)
+[import:34-46, lang:"python"](code/python/Tree_example.py)
 {% sample lang="scratch" %}
 This has not been implemented in your chosen language, so here is the Julia code
 [import:28-43, lang:"julia"](code/julia/Tree.jl)
@@ -154,7 +152,7 @@ In code, it looks like this:
 {% sample lang="js" %}
 [import:36-43, lang:"javascript"](code/javascript/tree.js)
 {% sample lang="py" %}
-[import:24-35, lang:"python"](code/python/Tree_example.py)
+[import:49-60, lang:"python"](code/python/Tree_example.py)
 {% sample lang="scratch" %}
 This has not been implemented in your chosen language, so here is the Julia code
 [import:45-56, lang:"julia"](code/julia/Tree.jl)
@@ -187,7 +185,7 @@ And this is exactly what Breadth-First Search (BFS) does! On top of that, it can
 {% sample lang="js" %}
 [import:45-52, lang:"javascript"](code/javascript/tree.js)
 {% sample lang="py" %}
-[import:37-48, lang:"python"](code/python/Tree_example.py)
+[import:63-74, lang:"python"](code/python/Tree_example.py)
 {% sample lang="scratch" %}
 This has not been implemented in your chosen language, so here is the Julia code
 [import:58-69, lang:"julia"](code/julia/Tree.jl)