Missing number in array [Easiest]

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Paytm, Ola-Cabs, Microsoft, Intuit, Cisco, Amazon

Given an array of size n-1 and given that there are numbers from 1 to n with one missing, the missing number is to be found.

Input:

The first line of input contains an integer T denoting the number of test cases.
The first line of each test case is N,size of array.
The second line of each test case contains N-1 input C[i],numbers in array.

Output:

Print the missing number in array.

Constraints:

1 ≤ T ≤ 200
1 ≤ N ≤ 1000
1 ≤ C[i] ≤ 1000

Example:

Input
2
5
1 2 3 5
10
1 2 3 4 5 6 7 8 10

Output
4
9

Algorithm:

1) Get the actual size of array (n in our solution)

2) Find the sum using the formula n*(n+1)/2

3) Subtract all elements of array from the above obtained sum to get ans 

Code;

import java.util.*;

import java.lang.*;

import java.io.*;

class Solution {

public static void main (String[] args) {

//code

Scanner sc = new Scanner (System.in);

int m = sc.nextInt();

for (int i=0;i<m;i++){

   int n = sc.nextInt();//size of array

   int sum = n*(n+1)/2;

   int [] arr = new int[n];

   for(int j=0;j<n-1;j++){

       arr[j]=sc.nextInt();

   }

            for (int k=0;k<n-1;k++){

                sum=sum-arr[k];

            }

            System.out.println(sum);

}

}

}