added a new solution

999_Practice/Day_48/Find_the_element_that_appears_once.cpp

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+// Java code to find the element
+// that occur only once
+
+class GFG {
+	// Method to find the element that occur only once
+	static int getSingle(int arr[], int n)
+	{
+		int ones = 0, twos = 0;
+		int common_bit_mask;
+
+		for (int i = 0; i < n; i++) {
+			/*"one & arr[i]" gives the bits that are there in
+			both 'ones' and new element from arr[]. We
+			add these bits to 'twos' using bitwise OR*/
+			twos = twos | (ones & arr[i]);
+
+			/*"one & arr[i]" gives the bits that are
+			there in both 'ones' and new element from arr[].
+			We add these bits to 'twos' using bitwise OR*/
+			ones = ones ^ arr[i];
+
+			/* The common bits are those bits which appear third time
+			So these bits should not be there in both 'ones' and 'twos'.
+			common_bit_mask contains all these bits as 0, so that the bits can
+			be removed from 'ones' and 'twos'*/
+			common_bit_mask = ~(ones & twos);
+
+			/*Remove common bits (the bits that appear third time) from 'ones'*/
+			ones &= common_bit_mask;
+
+			/*Remove common bits (the bits that appear third time) from 'twos'*/
+			twos &= common_bit_mask;
+		}
+		return ones;
+	}
+
+	// Driver method
+	public static void main(String args[])
+	{
+		int arr[] = { 3, 3, 2, 3 };
+		int n = arr.length;
+		System.out.println("The element with single occurrence is " + getSingle(arr, n));
+	}
+}
+// Code contributed by Rishab Jain