帮同学改的代码，简单易懂因为他是刚开始做 的写法：

#include <stdio.h>
#define MAX 10001
int main()
{int i, n;int sum1 = 0;int A1 = 0, A2 = 0, A3 = 0, A4 = 0;int a[MAX];scanf("%d", &n);for (i = 0; i < n; i++){scanf("%d", &a[i]);}//A1for (i = 0; i < n; i++){if (a[i] % 5 == 0 && a[i] % 2 == 0){sum1 = sum1 + a[i];A1++;}}if (A1 == 0){printf("N ");}elseprintf("%d ", sum1);//A2int sum = 0, flag = 1;for (i = 0; i < n; i++){if (a[i] % 5 == 1){A2++;a[i] = a[i] * flag;flag = -flag;sum = sum + a[i];}}if (A2 == 0){printf("N ");}elseprintf("%d ", sum);//A3int count = 0;for (i = 0; i < n; i++){if (a[i] % 5 == 2){count++;}}if (count == 0)printf("N ");elseprintf("%d ", count);//A4double he = 0, shu = 0;double m;for (i = 0; i < n; i++){if (a[i] % 5 == 3){he = a[i] + he;shu++;}}m = he / shu;if (shu == 0)printf("N ");elseprintf("%.1f ", m);//A5int maxn = -1;for (int i = 0; i < n; i++){if (a[i] % 5 == 4)if (a[i] > maxn)maxn = a[i];}if (maxn == -1)printf("N");elseprintf("%d", maxn);return 0;
}

拜拜！