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

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int i, j, A, N;
    int flag = 0, t;
    int sum[100000];

    scanf_s("%d %d", &A, &N);
    if (N == 0)
        printf("0\n");

    for (i = N, j = 0; i > 0; i--, j++)
    {
        t = A * i + flag;
        flag = t / 10;
        sum[j] = t % 10;
    }
    if (flag > 0)
    {
        sum[j] = flag;
        j++;
    }

    for (i = j - 1; i >= 0; i--)
        printf("%d", sum[i]);
    printf("\n");
    return 0;
}