Merge branch 'master' of https://github.com/YearOfProgramming/2017Cha…

…llenges

challenge_0/csharp/jfrancis2/README.md

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+# Challenge 0 - Hello World
+###### C#
+
+### 1. Approach to Solving the problem
+
+Output text "Hello World"
+
+### 2. How to compile and run this code
+
+From the /src directory, use `csc.exe hello.cs`
+
+### 3. How this program works
+
+Read the text! Hi :)

challenge_0/csharp/jfrancis2/src/hello.cs

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+using System;
+namespace HelloWorld
+{
+    class Hello 
+    {
+        static void Main() 
+        {
+            Console.WriteLine("Hello World!");
+            Console.WriteLine("Press any key to exit.");
+            Console.ReadKey();
+        }
+    }
+}

challenge_1/csharp/jfrancis2/README.md

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+# Challenge 1 - Reverse a String
+###### C#
+
+### 1. Approach to Solving the problem
+
+I had to work out how to get a string, then make it backwards. Turns out there are inbuilt functions for this.
+
+### 2. How to compile and run this code
+
+From the /src directory, use `csc.exe program.cs`
+
+### 3. How this program works
+
+Takes a string from the console input
+Converts to a char array
+Uses the 'System.Reverse' function to change the order of the characters
+Displays the reversed string

challenge_1/csharp/jfrancis2/src/program.cs

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+using System;
+namespace YOP2017
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            Console.WriteLine("Enter a string to reverse: ");
+            string input = Console.ReadLine();
+            Console.WriteLine("Your string in reverse: " + Program.reverseString(input));
+            Console.WriteLine("Press any key to exit.")
+            Console.ReadKey(true);
+        }
+        public static string reverseString(string input)
+        {
+            char[] arr = input.ToCharArray();
+            Array.Reverse(arr);
+            return new string(arr);
+        }
+    }
+}

challenge_14/c/karanchawla/README.md

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+```
+Karan Chawla
+Challenge 14
+```
+
+Approach: The aim here is to reverse a linked list. This is achieved by using three pointers - prev, current and next. Current moves along the linked list while the prev and next pointers are switched. Finally the head is set to the prev - completing the list reversal.

challenge_14/c/karanchawla/challenge_14.c

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+//Karan Chawla
+//Challenge 14
+
+#include <stdio.h>
+#include <stdlib.h>
+
+//Linked list node definition
+typedef struct node
+{
+	char c;
+	struct node* next;
+}Node;
+
+
+//utility function to create a new node
+Node* newNode(char c)
+{
+	Node* new_node = (Node*)malloc(sizeof(Node));
+	new_node->c = c;
+	new_node->next = NULL;
+
+	return new_node;
+}
+
+//utility function to add a new node to the linked list
+void push(Node** head_ref, char c)
+{
+	Node* new_node = newNode(c);
+
+	new_node->next = *head_ref;
+
+	*head_ref = new_node;
+}
+
+
+//function to reverse the linked list
+//prev->curr->next
+//changes prev to next and moves current along the linked list until NULL
+void reverseLinkedList(Node** head_ref)
+{
+	if (*head_ref==NULL)
+		return;
+
+	Node* prev = NULL;
+	Node* current = *head_ref;
+	Node* next;
+	while(current!=NULL)
+	{
+		next = current->next;
+		current->next = prev;
+		prev = current;
+		current = next;
+	}
+	*head_ref = prev;
+}
+
+//utility function to print linked list
+void printLinkedList(Node* head)
+{
+	while(head!=NULL)
+	{
+		printf("%c->", head->c);
+		head = head->next;
+	}
+	printf("NULL\n");
+}
+
+//driver program
+int main(void)
+{
+	Node* head = NULL;
+	//create a linked list with chars from "murder"
+	push(&head,'r');
+	push(&head,'e');
+	push(&head,'d');
+	push(&head,'r');
+	push(&head,'u');
+	push(&head,'m');
+
+	//print the linked list
+	printLinkedList(head);
+	//reverse the linked list
+	reverseLinkedList(&head);
+	//print the reversed linked list
+	printLinkedList(head);
+
+	return 0;
+}

challenge_7/python/ajschrier/MissingNumber.py

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+def builtInMethod(inputList):
+    for i in xrange(len(inputList)):
+        # Check if i is in list
+        if i not in inputList:
+            # Return number
+            return i
+    # Return 0 if none of the numbers meet the condition
+    return 0
+
+
+def sumMethod(inputList):
+    # find (n*n+1)/2
+    fullSum = (len(inputList) * (len(inputList) + 1)) / 2
+    # subtract sum of full range from supplied range
+    return fullSum - sum(inputList)
+
+
+def main():
+    pass
+
+
+if __name__ == '__main__':
+    main()

challenge_7/python/ajschrier/README.md

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+# Challenge 7 - Find the Missing Number
+
+*Python Version:* 2.7
+
+In a list 0..N, find which digit is missing.
+
+# Functions
+
+## builtInMethod
+
+**Input:** List
+**Output:** Integer
+
+Finds the integer 0 < x < N not present in list. The 'not in' syntax performs at O(N) according to [the Python Wiki](https://wiki.python.org/moin/TimeComplexity), so that is used to check the list for the value in the range. 
+
+**UPDATE**: 'not in' syntax is O(N), but the fact that it's in another loop makes the solution O(N^2). Thanks erocs.
+
+## sumMethod
+
+**Input:** List
+**Output:** Integer
+
+Uses the principle of sequential ranges (n*n+1)/2 to find the missing element. The sum of the input list is subtracted from the sum of the full range, exposing the missing element.

challenge_7/python/ajschrier/Test_MissingNumber.py

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+import MissingNumber
+import unittest
+
+
+class BuiltInTests(unittest.TestCase):
+    """tests for builtInMethod"""
+
+    def testMissing3(self):
+        self.assertEqual(MissingNumber.
+                         builtInMethod([0, 1, 2, 4]), 3)
+
+    def testMissing2(self):
+        self.assertEqual(MissingNumber.
+                         builtInMethod([1, 3, 4, 0]), 2)
+
+    def testNoMissingNumber(self):
+        self.assertEqual(MissingNumber.
+                         builtInMethod([1, 2, 3]), 0)
+
+    def testLongerList(self):
+        self.assertEqual(MissingNumber.
+                         builtInMethod([0, 1, 2, 3, 4, 5, 6, 8, 9, 10, 11,
+                                        12, 13, 14, 15, 16, 17, 18, 19,
+                                        20, 21, 22, 23, 24]), 7)
+
+    def testEvenLongerRandomList(self):
+        self.assertEqual(MissingNumber.
+                         builtInMethod([78, 53, 118, 99, 154, 5, 52, 184,
+                                       73, 17, 92, 107, 34, 159, 101, 30,
+                                       171, 95, 100, 54, 63, 169, 37, 45,
+                                       174, 158, 57, 0, 89, 61, 71, 188,
+                                       83, 18, 133, 149, 62, 151, 90, 3,
+                                       141, 126, 165, 179, 103, 166, 68,
+                                       177, 163, 190, 77, 55, 31, 187, 16,
+                                       91, 47, 93, 146, 147, 74, 185, 135,
+                                       102, 41, 125, 164, 12, 19, 168, 96,
+                                       23, 86, 194, 9, 132, 104, 122, 24,
+                                       144, 161, 117, 183, 196, 176, 155,
+                                       108, 172, 120, 160, 182, 50, 75, 22,
+                                       15, 49, 80, 127, 106, 20, 148, 139,
+                                       38, 134, 67, 123, 56, 88, 40, 186,
+                                       131, 76, 59, 21, 43, 4, 14, 115,
+                                       162, 199, 48, 128, 81, 39, 11, 97,
+                                       137, 153, 10, 65, 138, 114, 79, 6,
+                                       195, 156, 180, 8, 28, 60, 192, 42,
+                                       119, 64, 2, 200, 116, 129, 51, 178,
+                                       191, 121, 82, 143, 26, 110, 33, 136,
+                                       32, 175, 27, 150, 111, 105, 70, 157,
+                                       44, 13, 46, 170, 58, 69, 198, 193,
+                                       167, 25, 29, 181, 66, 72, 36, 87, 7,
+                                       98, 130, 152, 94, 189, 1, 84, 109,
+                                       113, 197, 145, 35, 124, 112, 173,
+                                       140, 142]), 85)
+
+
+class SumMethodTests(unittest.TestCase):
+    """tests for sumMethod"""
+
+    def testMissing3(self):
+        self.assertEqual(MissingNumber.
+                         sumMethod([0, 1, 2, 4]), 3)
+
+    def testMissing2(self):
+        self.assertEqual(MissingNumber.
+                         sumMethod([1, 3, 4, 0]), 2)
+
+    def testNoMissingNumber(self):
+        self.assertEqual(MissingNumber.
+                         sumMethod([1, 2, 3]), 0)
+
+    def testLongerList(self):
+        self.assertEqual(MissingNumber.
+                         sumMethod([0, 1, 2, 3, 4, 5, 6, 8, 9, 10, 11,
+                                    12, 13, 14, 15, 16, 17, 18, 19,
+                                    20, 21, 22, 23, 24]), 7)
+
+    def testEvenLongerRandomList(self):
+        self.assertEqual(MissingNumber.
+                         sumMethod([78, 53, 118, 99, 154, 5, 52, 184,
+                                    73, 17, 92, 107, 34, 159, 101, 30,
+                                    171, 95, 100, 54, 63, 169, 37, 45,
+                                    174, 158, 57, 0, 89, 61, 71, 188,
+                                    83, 18, 133, 149, 62, 151, 90, 3,
+                                    141, 126, 165, 179, 103, 166, 68,
+                                    177, 163, 190, 77, 55, 31, 187, 16,
+                                    91, 47, 93, 146, 147, 74, 185, 135,
+                                    102, 41, 125, 164, 12, 19, 168, 96,
+                                    23, 86, 194, 9, 132, 104, 122, 24,
+                                    144, 161, 117, 183, 196, 176, 155,
+                                    108, 172, 120, 160, 182, 50, 75, 22,
+                                    15, 49, 80, 127, 106, 20, 148, 139,
+                                    38, 134, 67, 123, 56, 88, 40, 186,
+                                    131, 76, 59, 21, 43, 4, 14, 115,
+                                    162, 199, 48, 128, 81, 39, 11, 97,
+                                    137, 153, 10, 65, 138, 114, 79, 6,
+                                    195, 156, 180, 8, 28, 60, 192, 42,
+                                    119, 64, 2, 200, 116, 129, 51, 178,
+                                    191, 121, 82, 143, 26, 110, 33, 136,
+                                    32, 175, 27, 150, 111, 105, 70, 157,
+                                    44, 13, 46, 170, 58, 69, 198, 193,
+                                    167, 25, 29, 181, 66, 72, 36, 87, 7,
+                                    98, 130, 152, 94, 189, 1, 84, 109,
+                                    113, 197, 145, 35, 124, 112, 173,
+                                    140, 142]), 85)
+
+
+if __name__ == '__main__':
+    unittest.main()