Longest Bitcoin Subsequence

Author: AmanPandey0198

Longest Bitonic Subsequence.java

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+class Main
+{
+    // Function to find the longest bitonic subsequence in an array
+    public static int calculateLBS(int[] nums)
+    {
+        int n = nums.length;
+ 
+        // base case
+        if (n == 0) {
+            return 0;
+        }
+ 
+        // `I[i]` store the length of the longest increasing subsequence,
+        // ending at `nums[i]`
+        int[] I = new int[n];
+ 
+        // `D[i]` stores the length of the longest decreasing subsequence,
+        // starting with `nums[i]`
+        int[] D = new int[n];
+ 
+        I[0] = 1;
+        for (int i = 1; i < n; i++)
+        {
+            for (int j = 0; j < i; j++)
+            {
+                if (nums[j] < nums[i] && I[j] > I[i]) {
+                    I[i] = I[j];
+                }
+            }
+            I[i]++;
+        }
+ 
+        D[n - 1] = 1;
+        for (int i = n - 2; i >= 0; i--)
+        {
+            for (int j = n - 1; j > i; j--)
+            {
+                if (nums[j] < nums[i] && D[j] > D[i]) {
+                    D[i] = D[j];
+                }
+            }
+            D[i]++;
+        }
+ 
+        // consider each element as a peak and calculate LBS
+        int lbs = 1;
+        for (int i = 0; i < n; i++) {
+            lbs = Integer.max(lbs, I[i] + D[i] - 1);
+        }
+ 
+        return lbs;
+    }
+ 
+    public static void main(String[] args)
+    {
+        int[] nums = { 4, 2, 5, 9, 7, 6, 10, 3, 1 };
+ 
+        System.out.print("The length of the longest bitonic subsequence is " +
+                calculateLBS(nums));
+    }
+}