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  • (Problem 28)Number spiral diagonals

    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=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
    ",sum);
    }
    
    int main()
    {
        countSum();
        return 0;
    }
    Answer:
    669171001
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  • 原文地址:https://www.cnblogs.com/acutus/p/3546131.html
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