1.大小写字母转换
#include <stdio.h>
void swap(char str[])
{
int i;
for (i = 0; str[i]; i )
{
if(str[i] >= 'A' && str[i] <= 'Z')
str[i] = 32;
else if(str[i] >= 'a' && str[i] <= 'z')
str[i] -= 32;
}
}
int main(int argc, const char *argv[])
{
char str[100] = "HelLo!!";
printf("%s\n", str);
swap(str);
printf("%s\n", str);
return 0;
}
2.把一个十进制的数变成二进制输出
#include <stdio.h>
void func(int num)
{
int arr[32];
int i = 0;
while(num) 遍历一个整数
{
arr[i ] = num % 2; //这个条件可以换成多样类型,比如 %10 可以把一个数分开;
num /= 2;
}
for(i = i - 1; i >= 0; i--)
printf("%d", arr[i]);
printf("\n");
}
int main(int argc, const char *argv[])
{
int num;
scanf("%d", &num);
func(num);
return 0;
}
3//输入一个日期,算出他是今年第几天;
#include <stdio.h>
int days[13] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
//
// 对闰月的判断
int is_leapyear(int year)
{
if((year % 400 == 0) || ((year % 4 == 0) && (year % 100 != 0))) 闰月的判断
return 1;
else
return 0;
}
int calc(int year, int month, int day)
{
int sum = 0;
int i;
for(i = 0; i < month; i )
{
sum = days[i];
}
sum = day;
if(month > 2 && is_leapyear(year)) //二月前的判断;
sum ;
return sum;
}
int main(int argc, const char *argv[])
{
int year, month, day;
scanf("%d %d %d", &year, &month, &day);
printf("%d\n",calc(year, month, day));
return 0;
}
4.实现两个字符串的链加
#include <stdio.h>
void mystrcat(char s1[], char s2[])
{
int i = 0;
int j = 0;
while(s1[i]) //遍历一个字符串到最后;
i ;
while(s2[j])
s1[i ] = s2[j ];
s1[i] = '\0';
}
int main(int argc, const char *argv[])
{
char s1[100] = "hello";
char s2[100] = "world";
mystrcat(s1, s2);
printf("%s\n", s1);
return 0;
}
5 用函数实现一个数的连加 //
#include <stdio.h>
int sum(int n)
{
if(n == 0)
return 0;
else
return n sum(n - 1); //连加的妙用
}
int main(int argc, const char *argv[])
{
printf("%d\n", sum(100));
return 0;
}
6.判断一个数是不是素数;
#include <stdio.h>
int is_prime(int n) //注意素数的条件
{
int i;
if(n < 2)
return 0;
for(i = 2; i < n; i )
{
if(n % i == 0)
return 0;
}
return 1;
}
int main(int argc, const char *argv[])
{
int n;
scanf("%d", &n);
//if(is_prime(n))
//printf("%d is prime\n", n);
//else
//printf("%d is not prime\n", n);
printf("%d is %s prime\n", n, is_prime(n) ? "":"not"); //?用
return 0;
}
7.判断三角形的三边
#include <stdio.h>
int is_tringle(int a, int b, int c)
{
//if((a b > c) && (a c > b) && (b c > a))
//return 1;
//else
//return 0;
if((a b <= c) || (a c <= b) || (b c <= a)) //条件的判断
return 0;
else
return 1;
}
int main(int argc, const char *argv[])
{
int a, b, c;
scanf("%d %d %d", &a, &b, &c);
if(is_tringle(a, b, c))
printf("is\n");
else
printf("not\n");
return 0;
}
8.三个数确定最大
#include <stdio.h>
int max_age(int, int, int);
int hour = 10;
int minute = 11 1;
int main(int argc, const char *argv[])
{
int hour = 10;
int minute = hour 1;
int m, n, p;
scanf("%d %d %d", &m, &n, &p);
printf("max = %d\n", max_age(m, n, p));
return 0;
}
int max_age(int a, int b, int c)
{
if(a < b) // 这种灵活的判断
a = b;
if(a < c)
return c;
return a;
}
9 实现N!
#include <stdio.h>
int factorial(int n)
{
if(n == 0)
return 1;
else
return n * factorial(n - 1); /这个
}
int main(int argc, const char *argv[])
{
int n;
scanf("%d", &n);
printf("%d\n", factorial(n));
return 0;
}
10自动钟表;
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