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:

669171001Completed 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;}