# Find a Missing Number From a Sequence of Consecutive Numbers | XOR Method

Input:  Array, arrA[] with a miss­ing num­ber and Range

Out­put : miss­ing number

Example:

```int A[] = { 1, 2, 7, 6, 3, 4 };
int range = 7;
Output: MIssing No is :5```

In our earlier approach ” Click Here ” we have seen the method where we had calculated the Sum of numbers, but this approach might fail when number goes beyond the integer range.

XOR method will better solution in that case.

Approach: – Time Complexity -O(N), Space Complexity – O(1)

• Do the XOR if 1 to n say its A
• Do the XOR of given array say its B
• Do the XOR of A and B will give the missing no

Code:

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 public class findMissingNo { // Do the XOR if 1 to n say its A // Do the XOR of given array say its B // Do the XOR of A and B will give the missing no public static int missingNo(int arrA[], int range) { int A = 0; int B = 0; for (int i = 1; i <= range; i++) { A = A ^ i; } for (int i = 0; i < arrA.length; i++) { B = B ^ arrA[i]; } return A ^ B; } public static void main(String[] args) { int A[] = { 1, 2, 7, 6, 3, 4 }; int range = 7; System.out.println("MIssing No is :" + missingNo(A, range)); } }

Output:

```MIssing No is :5
```

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