题解 | #数字阶梯求和#

#include<stdio.h>
#define MaxSize 290
int main() {
    int i, j,n, a, A[MaxSize];
    for (i = 0; i < MaxSize; i++)A[i] = 0;
    scanf("%d %d", &a, &n);
    for (i = 0; i < n; i++) {
        A[MaxSize-1 - i] = (n - i) * a;
    }
    
    for (j = MaxSize-1; j > 0; j--) {
        if (A[j] >= 10) {
            A[j - 1] += A[j] / 10;
            A[j] %= 10;
        }
    }
    for (i = 0; A[i] == 0; i++);
    for (; i < MaxSize; i++)printf("%d", A[i]);
    return 0;
}