2-06. 数列求和（20）

2-06. 数列求和（20）

//原始代码，测试点4一直超时# include <stdio.h>int main(){int r[10000]={0};int i, j;int a, n;scanf("%d%d",&a,&n);if(n == 0){printf("0\n");return 0; }for(i = 0; i < n; i ++){for(j = n-i; j > 0; j --){r[i] += a;if(r[i] > 9){r[i+1] += r[i]/10;r[i] = r[i]%10;}}}if(r[n] != 0){printf("%d",r[n]);}for(i = n-1; i >= 0; i --){printf("%d",r[i]);}return 0; }

修正后

# include <stdio.h>int main(){int r[100000];int a, n;int con = 0;//商int i;scanf("%d%d",&a,&n);if(n == 0){printf("0\n");return 0; }for(i = 0; (i < n) || (i==n&&con!=0); i ++){r[i] = (a*(n-i)+con)%10;con  = (a*(n-i)+con)/10;}for(i --; i >= 0; i --){printf("%d",r[i]);}return 0; }