Problem 28 Number spiral diagonals （规律题）

Number spiral diagonals

Problem 28

Starting with the number 1 and moving to the right in a clockwise direction a 5 by 5 spiral is formed as follows:

21 22 23 24 25

20  7  8  9 10

19  6  1  2 11

18  5  4  3 12
17 16 15 14 13
It can be verified that the sum of the numbers on the diagonals is 101.

What is the sum of the numbers on the diagonals in a 1001 by 1001 spiral formed in the same way?

Answer: 669171001 Completed on Fri, 28 Oct 2016, 18:05

题解：规律题....

代码：

#include<bits/stdc++.h>
using namespace std;
int main()
{
long long ans=1;
int count=0;
int k=2;
for(int i=3;i<=1001*1001;i+=k)
{
//cout<<i<<endl;
ans+=i;
count++;
if(count==4)
{
k+=2;
count=0;
}
}
cout<<ans<<endl;
return 0;
}