1+ package com .udemy .dsapart1 .recursion ;
2+ import java .util .Arrays ;
3+ import java .util .Scanner ;
4+ 5+ /**
6+ * Section 2 : Recursion Programming problems for -
7+ * - 1) Sum of Array elements using Recursion.
8+ * - 2) Factorial of a number using Recursion.
9+ * - 3) N-th number of Fibonacci Series using Recursion.
10+ *
11+ */
12+ public class ArraySumFactorialFobonaciWithRecursion {
13+ 14+ static double inputArr [];
15+ 16+ public static void main (String [] args ) {
17+ int sizeOfArr ;
18+ Scanner scInpObj = new Scanner (System .in );
19+ System .out .print ("\n Enter the size of Array : " );
20+ sizeOfArr = scInpObj .nextInt ();
21+ inputArr = new double [sizeOfArr ];
22+ System .out .println ("\n Enter the Array elements : " );
23+ pushElementsIntoArray (inputArr );
24+ System .out .println ("\n Input Array : " + Arrays .toString (inputArr ));
25+ 26+ System .out .println ("\n Sum of Array elements : " );
27+ System .out .println ("*************************************************" );
28+ int lastElementPosition =inputArr .length -1 ;
29+ double sumOfItems =findSumOfArrayElements (lastElementPosition );
30+ System .out .println (sumOfItems );
31+ 32+ System .out .print ("\n Enter the number to compute factoral : " );
33+ double inputNumToFact = scInpObj .nextDouble ();
34+ System .out .println ("*************************************************" );
35+ System .out .println ("\n Factorial of N : " );
36+ double factOfNth =calculateFactorialOfN (inputNumToFact );
37+ System .out .println (factOfNth );
38+ 39+ System .out .print ("\n N-th number of Fibonacci Series using Recursion : " );
40+ long nthNumInput = scInpObj .nextLong ();
41+ System .out .println ("\n *************************************************" );
42+ System .out .println ("" +nthNumInput +"th Fibonacci number : " );
43+ long fiboNumVal =getNthFibonaciNumber (nthNumInput );
44+ System .out .println (fiboNumVal );
45+ }
46+ 47+ 48+ /**
49+ * N-th number of Fibonacci Series using Recursion.
50+ * @param nthNumInput
51+ *
52+ */
53+ private static long getNthFibonaciNumber (long nthNumInput ) {
54+ if (nthNumInput == 0 || nthNumInput == 1 ) {
55+ return nthNumInput ;
56+ }
57+ return getNthFibonaciNumber (nthNumInput - 1 ) + getNthFibonaciNumber (nthNumInput - 2 );
58+ }
59+ 60+ 61+ /**
62+ * Factorial of a number using Recursion.
63+ * @param inputNumToFact
64+ *
65+ */
66+ private static double calculateFactorialOfN (double inputNumToFact ) {
67+ if (inputNumToFact == 0 || inputNumToFact == 1 ) {
68+ return 1 ;
69+ }
70+ return inputNumToFact * calculateFactorialOfN (inputNumToFact - 1 );
71+ }
72+ 73+ 74+ /**
75+ * Sum of Array elements using Recursion.
76+ * @param inputArr
77+ *
78+ */
79+ private static double findSumOfArrayElements (int n ) {
80+ if (n == 0 ) {
81+ return inputArr [n ];
82+ }
83+ return inputArr [n ] + findSumOfArrayElements (n - 1 );
84+ }
85+ 86+ 87+ private static void pushElementsIntoArray (double inputArr []) {
88+ Scanner scInpObj = new Scanner (System .in );
89+ for (int i = 0 ; i < inputArr .length ; i ++) {
90+ System .out .print ("\n Enter the element No " + (i + 1 ) + " : " );
91+ inputArr [i ] = scInpObj .nextDouble ();
92+ }
93+ }
94+ 95+ }
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