Missing Number

Task: Find the missing number from given an array of N numbers from 1 to N.

Example:

Input:

1

3

1 4 3

Output:

2

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Here is the Code:

Program in C++:

1. #include <iostream>
2. using namespace std;
3. 
   
4. int main() {
5. //number of test cases
6. int t;
7. scanf("%d\n",&t);
8. while(t--)
9. {
10.     int n;
11.     scanf("%d\n",&n);
12.     int a[n-1],sum=0;
13.     for(int i=0;i<n-1;i++)
14.     {
15.         scanf("%d\n",&a[i]);
16.         sum+=a[i];
17.     }
18.     int sn=(n*(n+1))/2;
19.     cout<<sn-sum<<endl;
20. }
21. return 0;
22. }

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Here is the Video: