Create FirstIndexOfEle.java

Author: akshayavb99

Course 2 - Data Structures in JAVA/Lecture 4 - Recursion I/FirstIndexOfEle.java

@@ -0,0 +1,54 @@
+/*
+Given an array of length N and an integer x, you need to find and return the first index of integer x present in the array. Return -1 if it is not present in the array.
+First index means, the index of first occurrence of x in the input array. Do this recursively. Indexing in the array starts from 0.
+
+Input Format :
+Line 1 : An Integer N i.e. size of array
+Line 2 : N integers which are elements of the array, separated by spaces
+Line 3 : Integer x
+
+Output Format :
+first index or -1
+
+Constraints :
+1 <= N <= 10^3
+
+Sample Input :
+4
+9 8 10 8
+8
+Sample Output :
+1
+*/
+
+
+public class FirstIndexOfEle {
+
+	public static int firstIndex(int input[], int x) {
+		return firstIndex(input,x,0);
+	}
+    
+    public static int firstIndex(int input[], int x, int si)
+    {
+        if (si==input.length-1)
+        {
+            if (input[si]==x)
+            {
+                return si;
+            }
+            else
+            {
+                return -1;
+            }
+        }
+        
+        if (input[si]==x)
+        {
+            return si;
+        }
+        
+        int smallIdx=firstIndex(input,x,si+1);
+        return smallIdx;
+    }
+	
+}