efficient approch for fiding missing element in array

Array/missingelementInArr.java

@@ -2,14 +2,25 @@
 
 public class missingelementInArr {
     // naive approch findng missing element in array with timeComplexity is theta(n) and auxullary space is theta(1) but one problem for large size array we will get error like overflow 
-    static int missNumber(int arr[]){
+   /*  static int missNumber(int arr[]){
         int n = arr.length;
         int n_elem_sum=(n+1)*(n+2)/2;
         for(int i=0;i<n;i++){
             n_elem_sum-=arr[i];
         }
         return n_elem_sum;
     }
+    */
+    static int missNumber(int arr[]){
+        int n = arr.length;
+        int res1 = arr[0];
+        int res2 = 1;
+        for(int i=1; i<n; i++)
+            res1^=arr[i];
+        for(int i=2; i<=n+1; i++)
+            res2^=i;
+        return res1^res2;
+    }
     public static void main(String[] args) {
         int arr[] = {1,2,3,5,6};
         System.out.println(missNumber(arr));