added subsequenceRecursive.js file under Recursion

Author: chiranjeev-thapliyal

Recursive/SubsequenceRecursive.js

@@ -0,0 +1,32 @@
+/*
+ * Problem Statement: Find all distinct, non-empty subsequence of given string in lexicographical order using recursive approach.
+ *
+ * What is subsequence?
+ * A Subsequence is sequence obtained by deleting some or no elements without changing the order of elements
+ * Example: Given a string = "abcd"
+ * 1. "abc" is a subsequence
+ * 2. "abd" is a subsequence
+ * 3. But "ba" is not a subsequence (because order is changed)
+ *
+ * What is lexicographical order?
+ * In simple terms, lexicographical order is dictionary order.
+ * Example: Given a string = "abcd"
+ * 1. "abc" will come before "abcd".
+ * 2. "abd" will come before "ac".
+ *
+ * References for meaning of subsequence & lexicographical:
+ * https://en.wikipedia.org/wiki/Subsequence
+ * https://en.wikipedia.org/wiki/Lexicographic_order
+ */
+
+const subsequence = (str, seq, low) => {
+  if (low <= str.length && str.length !== '') {
+    console.log(seq)
+  }
+  for (let i = low; i < str.length; i++) {
+    subsequence(str, seq + str[i], i + 1)
+  }
+}
+
+const str = 'abcd'
+subsequence(str, '', 0)