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?
#include<stdio.h>
#include<string.h>
#include<math.h>
#include<ctype.h>
#include<stdlib.h>
#include<stdbool.h>
void countSum()
{
int i=3;
int sum=1;
int n=(1001+1)/2-1;
while(n--)
{
int t=i*i;
sum+=(4*t-(i-1)*6);
i=i+2;
}
printf("%d\n",sum);
}
int main()
{
countSum();
return 0;
}
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Answer:
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669171001 |