2-6 数列求和

题目链接：https://pintia.cn/problem-sets/434/problems/5654

代码如下：代码是参考这篇文章的：https://blog.csdn.net/VisDate/article/details/50950019

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 
 4 int main()
 5 {
 6     int i, j, A, N;
 7     int flag = 0, t;
 8     int sum[100000];
 9 
10     scanf_s("%d %d", &A, &N);
11     if (N == 0)
12         printf("0
");
13 
14     for (i = N, j = 0; i > 0; i--, j++)
15     {
16         t = A * i + flag;
17         flag = t / 10;
18         sum[j] = t % 10;
19     }
20     if (flag > 0)
21     {
22         sum[j] = flag;
23         j++;
24     }
25 
26     for (i = j - 1; i >= 0; i--)
27         printf("%d", sum[i]);
28     printf("
");
29     return 0;
30 }