C语言基础练习3

1.输入一行字符，分别统计出其中英文字母、空格、数字和其它字符的个数

#include<stdio.h>  
#include<string.h> 

int main()
{
	int letter = 0, space = 0, number = 0, other = 0, i;
	char ch[100];
	gets_s(ch);
	for (i = 0;i<strlen(ch); i++)
	{
		if (ch[i] >= 'A'&&ch[i] <= 'Z' || ch[i] >= 'a'&&ch[i] <= 'z')
			letter++;
		else if (ch[i] == ' ')
			space++;
		else if (ch[i] <= '9'&&ch[i] >= '0')
			number++;
		else
			other++;
	}
	printf("letter=%d\nspace=%d\nnumber=%d\nother=%d\n", letter, space, number, other);

}

2.求Σ(k=1~100)k+Σ(k=1~50)k^2+Σ(k=1~10)1/k

#include<stdio.h>

int main()
{
	int k,a=0,b=0,c=0;
	for (k = 1; k <= 100; k++)
		a = a + k;
	for (k = 1; k <= 50; k++)
		b = b + k*k;
		for (k = 1; k <= 10;k++)
		c = c + 1 / k;
	printf("%d\n", a + b + c);
    return 0;
}

3.输出所有的“水仙花”数

#include<stdio.h>

int main()
{
	int n,i,j,k;
	for (n = 100; n <= 999; n++)
	{
		i = n / 100;
		j = (n - i * 100) / 10;
		k = n % 10;
		if (n == i*i*i + j*j*j + k*k*k)
			printf("%d ", n);
	}
	printf("\n");
    return 0;
}