Change project structure to a Maven Java project + Refactor (#2816)

src/main/java/com/thealgorithms/dynamicprogramming/LongestAlternatingSubsequence.java

@@ -0,0 +1,70 @@
+package com.thealgorithms.dynamicprogramming;
+
+/*
+
+ * Problem Statement: - 
+ * Find Longest Alternating Subsequence
+
+ * A sequence {x1, x2, .. xn} is alternating sequence if its elements satisfy one of the following relations : 
+
+   x1 < x2 > x3 < x4 > x5 < …. xn or 
+   x1 > x2 < x3 > x4 < x5 > …. xn
+ */
+public class LongestAlternatingSubsequence {
+
+    /* Function to return longest alternating subsequence length*/
+    static int AlternatingLength(int arr[], int n) {
+        /*
+
+		las[i][0] = Length of the longest
+			alternating subsequence ending at
+			index i and last element is
+			greater than its previous element
+
+		las[i][1] = Length of the longest
+			alternating subsequence ending at
+			index i and last element is
+			smaller than its previous
+			element 
+
+         */
+        int las[][] = new int[n][2]; // las = LongestAlternatingSubsequence
+
+        for (int i = 0; i < n; i++) {
+            las[i][0] = las[i][1] = 1;
+        }
+
+        int result = 1; // Initialize result
+
+        /* Compute values in bottom up manner */
+        for (int i = 1; i < n; i++) {
+
+            /* Consider all elements as previous of arr[i]*/
+            for (int j = 0; j < i; j++) {
+
+                /* If arr[i] is greater, then check with las[j][1] */
+                if (arr[j] < arr[i] && las[i][0] < las[j][1] + 1) {
+                    las[i][0] = las[j][1] + 1;
+                }
+
+                /* If arr[i] is smaller, then check with las[j][0]*/
+                if (arr[j] > arr[i] && las[i][1] < las[j][0] + 1) {
+                    las[i][1] = las[j][0] + 1;
+                }
+            }
+
+            /* Pick maximum of both values at index i */
+            if (result < Math.max(las[i][0], las[i][1])) {
+                result = Math.max(las[i][0], las[i][1]);
+            }
+        }
+
+        return result;
+    }
+
+    public static void main(String[] args) {
+        int arr[] = {10, 22, 9, 33, 49, 50, 31, 60};
+        int n = arr.length;
+        System.out.println("Length of Longest " + "alternating subsequence is " + AlternatingLength(arr, n));
+    }
+}