Author: Aryan KD
Tester: Aryan KD
Editorialist: Aryan KD
DIFFICULTY:
CAKEWALK, SIMPLE, EASY.
PREREQUISITES:
Math .
PROBLEM:
Series of natural number is given .
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 …… 10^9
you have to find a missing number if sum of first N number is given
for example :
N=5, Sum=10
you have to find missing term in first 5 number
according to above series sum of first 5 number is 15, and if we subtract 5 from it then sum becomes 10 hence the missing number is 5 .
EXPLANATION:
You simply given N and sum of first N number in that one term is missing so if we subtract the sum given in question with original sum that given we will get our answer.
for example
N=5 sum=10
Sum of first N number is 15 but sum is given 10 so if we subtract 10 with 15 we will get our answer that is 5
formula for sum of first N natural number is (N*(N+1))/2
SOLUTIONS:
Setter's Solution
#include<bits/stdc++.h>
using namespace std;
void testcase()
{
long long int n,sum;
cin>>n>>sum;
long long int k=(n*(n+1))/2;
long long int pp=k-sum;
cout<<pp;
}
int main()
{
int t;
cin>>t;
while(t–)
{
testcase();
cout<<endl;
}
return 0;
}
Tester's Solution
#include<bits/stdc++.h>
using namespace std;
void testcase()
{
long long int n,sum;
cin>>n>>sum;
long long int k=(n*(n+1))/2;
long long int pp=k-sum;
cout<<pp;
}
int main()
{
int t;
cin>>t;
while(t–)
{
testcase();
cout<<endl;
}
return 0;
}
Editorialist's Solution
#include<bits/stdc++.h>
using namespace std;
void testcase()
{
long long int n,sum;
cin>>n>>sum;
long long int k=(n*(n+1))/2;
long long int pp=k-sum;
cout<<pp;
}
int main()
{
int t;
cin>>t;
while(t–)
{
testcase();
cout<<endl;
}
return 0;
}