刷题 26-30

二十六、求数组对角线之和

#define SIZE 3
int main()
{
	int arr[SIZE][SIZE] =
	{
		1,2,3,
		4,5,6,
		7,8,9
	};
	int sum = 0;
	for (int i = 0; i < SIZE; i++)
	{
		sum = sum + arr[i][i];
	}
	for (int i = 0; i < SIZE; i++)
	{
		sum += arr[i][SIZE - 1 - i];
	}
	sum = sum - arr[SIZE/ 2][SIZE / 2];
	printf("对角线元素之和为: %d\n", sum);

	return 0;
}

二十七、输出100以内的素数

#include 
#include 

bool isPrime(int number) {
    if (number <= 1) {
        return false;
    }

    for (int i = 2; i * i <= number; i++) {
        if (number % i == 0) {
            return false;
        }
    }

    return true;
}

int main() {
    printf("Prime numbers within 100:\n");

    for (int i = 2; i <= 100; i++) {
        if (isPrime(i)) {
            printf("%d ", i);
        }
    }

    printf("\n");

    return 0;
}