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?
原题大意：
从数字1开始向右顺时针方向移动，可以得到如下的5×5的螺旋：
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
可以算出对角线上数字之和是101. 1001×1001的螺旋中对角线上数字之和是多少？
//（Problem 28）Number spiral diagonals
// Completed on Thu, 25 Jul 2013, 14:31
// Language: C
//
// 版权所有（C）acutus (mail: acutus@126.com)
// 博客地址：http://www.cnblogs.com/acutus/ #include<stdio.h>
void countSum()
{
int i=;
int sum=;
int n=(+)/-;
while(n--)
{
int t=i*i;
sum+=(*t-(i-)*);
i=i+;
}
printf("%d\n",sum);
} int main()
{
countSum();
return ;
}
|
Answer:
|
669171001 |