從數字1開始向右順時針方向移動,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
可以算出對角線上數字之和是101.
1001×1001的螺旋中對角線上數字之和是多少?
public class Project28
{
public static void main(String[] args)
{
long start = System.currentTimeMillis();
System.out.print("answer: ");
howmany();
long end = System.currentTimeMillis();
System.out.print("time: ");
System.out.println(end - start);
}
static void howmany()
{
int sum = 1;
int add = 0;
int n = 0;
for (int i = 1; i < 1001 * 1001; )
{
if (n % 4 == 0)
{
add += 2;
}
n++;
i += add;
sum += i;
}
System.out.println(sum);
}
}
answer: 669171001
time: 0