Refactored all solutions

RodneyShag · Apr 5, 2017 · decc8e7 · decc8e7
1 parent 5f4c2f4
commit decc8e7
Show file tree

Hide file tree

Showing 135 changed files with 847 additions and 848 deletions.
diff --git a/10 Days of Statistics/Day 0 - Mean, Median, and Mode/Solution.java b/10 Days of Statistics/Day 0 - Mean, Median, and Mode/Solution.java
@@ -6,15 +6,12 @@
 import java.util.Arrays;
 import java.util.HashMap;
 
-/* Runtime: O(n log n) due to sorting */
+// Time Complexity: O(n log n) due to sorting
 public class Solution {
-
     public static void main(String[] args) {
-
-        /* Read input: Create and fill array */
+        /* Save input */
         Scanner scan = new Scanner(System.in);
         int size = scan.nextInt();
-
         int [] array = new int[size];
         for (int i = 0; i < size; i++) {
             array[i] = scan.nextInt();
@@ -39,26 +36,14 @@ public static void main(String[] args) {
             median = array[size / 2];
         }
 
-        /* Calculate Mode */        
+        /* Calculate Mode - if there's a tie, choose the smaller number */
         HashMap<Integer, Integer> map = new HashMap<>();
         int maxOccurrences = 0;
         int mode = Integer.MAX_VALUE;
-
         for (int num : array) {
-            /* Update occurrences for this number */
-            int occurrences;
-            if (map.containsKey(num)) {
-                occurrences = map.get(num) + 1;
-            } else {
-                occurrences = 1;
-            }
-            map.put(num, occurrences);
-
-            /* Update our mode. If there's a tie, choose the smaller number */
-            if (occurrences > maxOccurrences) {
-                maxOccurrences = occurrences;
-                mode = num;
-            } else if (occurrences == maxOccurrences && num < mode) { // this does the tie-breaking
+            map.merge(num, 1, Integer::sum);
+            int occurrences = map.get(num);
+            if (occurrences > maxOccurrences || (occurrences == maxOccurrences && num < mode)) {
                 maxOccurrences = occurrences;
                 mode = num;
             }

diff --git a/10 Days of Statistics/Day 0 - Weighted Mean/Solution.java b/10 Days of Statistics/Day 0 - Weighted Mean/Solution.java
@@ -5,10 +5,8 @@
 import java.util.Scanner;
 
 public class Solution {
-
     public static void main(String[] args) {
-
-        /* Read and save data */
+        /* Save input */
         Scanner scan = new Scanner(System.in);
         int size = scan.nextInt();
         int [] elements = new int[size];
@@ -28,7 +26,6 @@ public static void main(String[] args) {
             total += elements[i] * weights[i];
             totalWeights += weights[i];
         }
-
         double weightedMean = (double) total / totalWeights;
         System.out.format("%.1f", weightedMean);
     }

diff --git a/10 Days of Statistics/Day 1 - Interquartile Range/Solution.java b/10 Days of Statistics/Day 1 - Interquartile Range/Solution.java
@@ -6,17 +6,15 @@
 import java.util.Arrays;
 
 public class Solution {
-
     public static void main(String[] args) {
-        /* Read and save input */
+        /* Save input */
         Scanner scan = new Scanner(System.in);
         int size = scan.nextInt();
         int [] element = new int[size];
         int [] frequency = new int[size];
         for (int i = 0; i < size; i++) {
             element[i] = scan.nextInt();
         }
-
         int numElements = 0;
         for (int i = 0; i < size; i++) {
             frequency[i] = scan.nextInt();
@@ -35,14 +33,13 @@ public static void main(String[] args) {
         }
         Arrays.sort(data);
 
-        /* Works with both even and odd length arrays */
+        /* Calculate interquartile range */
         double q1 = findMedian(data, 0, data.length / 2 - 1);
         double q3 = findMedian(data, (data.length + 1) / 2, data.length - 1);
-
         System.out.println(q3 - q1);
     }
 
-    /* Treats elements from "start" to "end" as an array and calculates its median */
+    /* Treats elements from "start" to "end" (inclusive) as an array and calculates its median */
     private static double findMedian(int [] array, int start, int end) {
         if ((end - start) % 2 == 0) { // odd number of elements
             return (array[(end + start) / 2]);

diff --git a/10 Days of Statistics/Day 1 - Quartiles/Solution.java b/10 Days of Statistics/Day 1 - Quartiles/Solution.java
@@ -6,33 +6,19 @@
 import java.util.Arrays;
 
 public class Solution {
-
     public static void main(String[] args) {
         int [] array = getValues();
         Arrays.sort(array);
 
-        /* Works with both even and odd length arrays */
         int q1 = findMedian(array, 0, array.length / 2 - 1);
         int q2 = findMedian(array, 0, array.length - 1);
         int q3 = findMedian(array, (array.length + 1) / 2, array.length - 1);
 
-        /* Print output */
         System.out.println(q1);
         System.out.println(q2);
         System.out.println(q3);
     }
 
-    /* Treats elements from "start" to "end" as an array and calculates its median */
-    private static int findMedian(int [] array, int start, int end) {
-        if ((end - start) % 2 == 0) { // odd number of elements
-            return (array[(end + start) / 2]);
-        } else { // even number of elements
-            int value1 = array[(end + start) / 2];
-            int value2 = array[(end + start) / 2 + 1];
-            return Math.round((value1 + value2) / 2); 
-        }
-    }
-
     /* Creates array from input */
     private static int [] getValues() {
         Scanner scan = new Scanner(System.in);
@@ -44,4 +30,15 @@ private static int findMedian(int [] array, int start, int end) {
         scan.close();
         return array;
     }
+
+    /* Treats elements from "start" to "end" (inclusive) as an array and calculates its median */
+    private static int findMedian(int [] array, int start, int end) {
+        if ((end - start) % 2 == 0) { // odd number of elements
+            return (array[(end + start) / 2]);
+        } else { // even number of elements
+            int value1 = array[(end + start) / 2];
+            int value2 = array[(end + start) / 2 + 1];
+            return Math.round((value1 + value2) / 2); 
+        }
+    }
 }
diff --git a/10 Days of Statistics/Day 1 - Standard Deviation/Solution.java b/10 Days of Statistics/Day 1 - Standard Deviation/Solution.java
@@ -5,9 +5,8 @@
 import java.util.Scanner;
 
 public class Solution {
-
     public static void main(String[] args) {
-        /* Read and save input */
+        /* Save input */
         Scanner scan = new Scanner(System.in);
         int size = scan.nextInt();
         int [] array = new int[size];

diff --git a/10 Days of Statistics/Day 4 - Binomial Distribution I/Solution.java b/10 Days of Statistics/Day 4 - Binomial Distribution I/Solution.java
@@ -3,12 +3,10 @@
 // HackerRank: hackerrank.com/rshaghoulian
 
 public class Solution {
-
     public static void main(String[] args) {
-        double ratio = 1.09;
-
-        double p = ratio / (1 + ratio);
-        int    n = 6;
+        double ratio = 1.09; // hardcoded value
+        double p     = ratio / (1 + ratio);
+        int    n     = 6;
 
         /* Calculate result */
         double result = 0;
@@ -32,7 +30,7 @@ private static Long combinations(int n, int x) {
         return factorial(n) / (factorial(x) * factorial(n - x));
     }
 
-    private static Long factorial (int n) {
+    private static Long factorial(int n) {
         if (n < 0) {
             return null;
         }

diff --git a/10 Days of Statistics/Day 4 - Binomial Distribution II/Solution.java b/10 Days of Statistics/Day 4 - Binomial Distribution II/Solution.java
@@ -3,7 +3,6 @@
 // HackerRank: hackerrank.com/rshaghoulian
 
 public class Solution {
-
     public static void main(String[] args) {
         /* Values given in problem statement */
         double p = 0.12;
@@ -35,7 +34,7 @@ private static Long combinations(int n, int x) {
         return factorial(n) / (factorial(x) * factorial(n - x));
     }
 
-    private static Long factorial (int n) {
+    private static Long factorial(int n) {
         if (n < 0) {
             return null;
         }

diff --git a/10 Days of Statistics/Day 4 - Geometric Distribution I/Solution.java b/10 Days of Statistics/Day 4 - Geometric Distribution I/Solution.java
@@ -5,9 +5,8 @@
 import java.util.Scanner;
 
 public class Solution {
-
     public static void main(String[] args) {
-        /* Read and save input */
+        /* Save input */
         Scanner scan = new Scanner(System.in);
         int numerator   = scan.nextInt();
         int denominator = scan.nextInt();
@@ -30,7 +29,7 @@ private static Long combinations(int n, int x) {
         return factorial(n) / (factorial(x) * factorial(n - x));
     }
 
-    private static Long factorial (int n) {
+    private static Long factorial (int n){
         if (n < 0) {
             return null;
         }

diff --git a/10 Days of Statistics/Day 4 - Geometric Distribution II/Solution.java b/10 Days of Statistics/Day 4 - Geometric Distribution II/Solution.java
@@ -5,9 +5,8 @@
 import java.util.Scanner;
 
 public class Solution {
-
     public static void main(String[] args) {
-        /* Read and save input */
+        /* Save input */
         Scanner scan = new Scanner(System.in);
         int numerator   = scan.nextInt();
         int denominator = scan.nextInt();
@@ -34,7 +33,7 @@ private static Long combinations(int n, int x) {
         return factorial(n) / (factorial(x) * factorial(n - x));
     }
 
-    private static Long factorial (int n) {
+    private static Long factorial(int n) {
         if (n < 0) {
             return null;
         }

diff --git a/10 Days of Statistics/Day 5 - Normal Distribution I/Solution.java b/10 Days of Statistics/Day 5 - Normal Distribution I/Solution.java
@@ -3,7 +3,6 @@
 // HackerRank: hackerrank.com/rshaghoulian
 
 public class Solution {
-
     public static void main(String[] args) {
         double mean = 20;
         double std  = 2;

diff --git a/10 Days of Statistics/Day 5 - Normal Distribution II/Solution.java b/10 Days of Statistics/Day 5 - Normal Distribution II/Solution.java
@@ -3,7 +3,6 @@
 // HackerRank: hackerrank.com/rshaghoulian
 
 public class Solution {
-
     public static void main(String[] args) {
         double mean = 70;
         double std  = 10;

diff --git a/10 Days of Statistics/Day 5 - Poisson Distribution I/Solution.java b/10 Days of Statistics/Day 5 - Poisson Distribution I/Solution.java
@@ -5,9 +5,8 @@
 import java.util.Scanner;
 
 public class Solution {
-
     public static void main(String[] args) {
-        /* Read and save input */
+        /* Save input */
         Scanner scan = new Scanner(System.in);
         double lambda = scan.nextDouble();
         int k = scan.nextInt();
@@ -20,7 +19,7 @@ private static double poisson(int k, double lambda) {
         return (Math.pow(lambda, k) * Math.pow(Math.E, -1 * lambda)) / factorial(k);
     }
 
-    private static Long factorial (int n) {
+    private static Long factorial(int n) {
         if (n < 0) {
             return null;
         }

diff --git a/10 Days of Statistics/Day 5 - Poisson Distribution II/Solution.java b/10 Days of Statistics/Day 5 - Poisson Distribution II/Solution.java
@@ -9,9 +9,8 @@
     https://www.hackerrank.com/challenges/s10-poisson-distribution-2/forum/comments/176962
 */
 public class Solution {
-
     public static void main(String[] args) {
-        /* Read and save input */
+        /* Save input */
         Scanner scan = new Scanner(System.in);
         double A = scan.nextDouble();
         double B = scan.nextDouble();

diff --git a/10 Days of Statistics/Day 6 - The Central Limit Theorem I/Solution.java b/10 Days of Statistics/Day 6 - The Central Limit Theorem I/Solution.java
@@ -3,7 +3,6 @@
 // HackerRank: hackerrank.com/rshaghoulian
 
 public class Solution {
-
     public static void main(String[] args) {
         double mean      = 205;
         double std       = 15;

diff --git a/10 Days of Statistics/Day 6 - The Central Limit Theorem II/Solution.java b/10 Days of Statistics/Day 6 - The Central Limit Theorem II/Solution.java
@@ -3,7 +3,6 @@
 // HackerRank: hackerrank.com/rshaghoulian
 
 public class Solution {
-
     public static void main(String[] args) {
         double ticketsLeft = 250;
         int    n           = 100;

diff --git a/10 Days of Statistics/Day 7 - Pearson Correlation Coefficient I/Solution.java b/10 Days of Statistics/Day 7 - Pearson Correlation Coefficient I/Solution.java
@@ -5,9 +5,8 @@
 import java.util.Scanner;
 
 public class Solution {
-
     public static void main(String[] args) {
-        /* Read and save input */
+        /* Save input */
         Scanner scan = new Scanner(System.in);
         int size = scan.nextInt();
         double [] xs = new double[size];
@@ -18,10 +17,11 @@ public static void main(String[] args) {
         for (int i = 0; i < size; i++) {
             ys[i] = scan.nextDouble();
         }
+        scan.close();
 
         System.out.println(pearson(xs, ys));
     }
-
+    
     /* Calculates Pearson coefficient */
     private static Double pearson(double [] xs, double [] ys) {
         if (xs == null || ys == null || xs.length != ys.length) {
@@ -62,3 +62,4 @@ private static Double standardDeviation(double [] array) {
         return Math.sqrt(variance);
     }
 }
+