Added Solution - GfG to GitHub

Difficulty: Easy/Missing And Repeating/missing-and-repeating.java

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+//{ Driver Code Starts
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.ArrayList; // Import ArrayList
+import java.util.Stack;
+
+public class Main {
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+
+        int t = Integer.parseInt(br.readLine());
+
+        while (t-- > 0) {
+            String input = br.readLine();
+            String[] inputs = input.split(" ");
+            int[] arr = new int[inputs.length];
+
+            for (int i = 0; i < inputs.length; i++) {
+                arr[i] = Integer.parseInt(inputs[i]);
+            }
+
+            // Get the result as an ArrayList<Integer>
+            ArrayList<Integer> ans = new Solution().findTwoElement(arr);
+            System.out.println(ans.get(0) + " " + ans.get(1));
+            System.out.println("~");
+        }
+    }
+}
+
+// } Driver Code Ends
+
+
+// User function Template for Java
+
+ class Solution {
+
+    ArrayList<Integer> findTwoElement(int arr[]) {
+
+        int n = arr.length;
+        ArrayList<Integer> result = new ArrayList<>();
+
+        long expectedSum = (long) n * (n + 1) / 2;
+        long expectedSumOfSquares = (long) n * (n + 1) * (2 * n + 1) / 6;
+
+        // Calculate the actual sum and sum of squares from the array
+        long actualSum = 0;
+        long actualSumOfSquares = 0;
+
+        for (int i = 0; i < n; i++) {
+            actualSum += arr[i];
+            actualSumOfSquares += (long) arr[i] * arr[i];
+        }
+
+        // Calculate the differences
+        long sumDifference = expectedSum - actualSum; // missing - repeating
+        long squareSumDifference = expectedSumOfSquares - actualSumOfSquares; // missing^2 - repeating^2
+
+        // Solve for missing and repeating using the equations
+        long sumPlusDifference = squareSumDifference / sumDifference; // missing + repeating
+
+        int missing = (int) (sumDifference + sumPlusDifference) / 2;
+        int repeating = (int) (sumPlusDifference - missing);
+
+        // Add the results to the ArrayList
+        result.add(repeating);
+        result.add(missing);
+
+        return result;
+    }
+}