练一练_1

 打印100~200 之间的素数

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
int main() {
	int  num = 101;
	int i,count=0;
	for (num = 101; num <= 200; num +=2)
	{
		int t = 0;
		t = sqrt(num);
		for (i = 2; i <= t; i++) {
			if (num % i == 0)
				break;
		}
		if (i >=t + 1)
		{
			count++;
			printf("%d  ", num);
		}

	if (count % 7 == 0)
			printf("\n");
	}
	printf("\n");
	printf("count=%d\n", count);
	
	system("pause");
	return 0;	
}

输出乘法口诀表

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

int main() {
	int i, j,k;
	for (i = 1; i < 10; i++) {
		for (j = 1; j <= i; j++) {
			k = i*j;
			printf("%d*%d=%2d  ", j, i, k);
		}
		printf("\n");
	}
	system("pause");
	return 0;
}	

判断1000年---2000年之间的闰年

#include<stdio.h>
#include<stdlib.h>
int main() {
	int year = 1000;
	int n = 0;
	for (year = 1000; year <= 2000; year+=4) {
	
		if (year % 4 == 0&&year%100!=0||year%400==0) {
			printf("%d ", year);
			n++;
		}
		if (n % 10== 0)
			printf("\n");
}
	printf("\n");
	printf("n=%d", n);
	system("pause");
	return 0;
}