if_switch & 输入输出函数的格式 _0208

//1.#测试无break
#include <stdio.h>
int main(int argc, const char *argv[])
{
    int a=0;
    switch(a)
    {
        case 0:printf("a is a zero.\n");
        case 1:printf("a is one.\n");
        default:printf("a is not a zero or one.\n");
    }
    return 0;
}

//2.#输入一个分数，显示其等级
#include <stdio.h>

int main(int argc, const char *argv[])
{

    int i;
    printf("enter a scole:");
    scanf("%d",&i);
    switch(i)
    {
        case 0:printf("E\n");break;
        case 1:printf("D\n");break;
        case 2:printf("C\n");break;
        case 3:printf("B\n");break;
        case 4:printf("A\n");break;
        default:printf("error entering!(0~4)\n");
    }
    return 0;
}

//3.#输入0～100,显示其等级
#include <stdio.h>

int main(int argc, const char *argv[])
{
    int sc,n;
    printf("enter a scole:");
    scanf("%d",&sc);
    n=sc/10;
    switch(n)
    {
        case 10:printf("100\n");break;
        case 9:printf("90~99\n");break;
        case 8:printf("80~89\n");break;
        case 7:printf("70~79\n");break;
        case 6:printf("60~69\n");break;
        case 5:
        case 4:
        case 3:
        case 2:
        case 1:
        case 0:printf("not ok!\n");break;
        default:printf("error entering!!!(0~100)\n");
    }
    return 0;
}

//4#输入一个表达式，实现四则运算
#include <stdio.h>

int main(int argc, const char *argv[])
{
    int a,b;
    char ch;
    printf("enter an operation:");
    scanf("%d%c%d",&a,&ch,&b);
    switch(ch)
    {
        case '+':printf("%d+%d=%d\n",a,b,a+b);break;
        case '-':printf("%d-%d=%d\n",a,b,a-b);break;
        case '*':printf("%d*%d=%d\n",a,b,a*b);break;
        case '/' :printf("%d/%d=%d\n",a,b,a/b);break;
        default:printf("illegal operator!\n");
    }
    return 0;
}

//5#用终端模拟一个时钟，用终端打印时间，指定开始时间为23:59:50，显示格式为xx:xx:xx。(提示：sleep(1)用来延时一秒)。
#include <stdio.h>

int main(int argc, const char *argv[])
{
    int h=23,m=59,s=55;
    while(1)
    {
        printf("\r%02d:%02d:%02d",h,m,s);
        fflush(stdout);
        sleep(1);
        s++;
        if(s==60)
        {
            s=0;
            m++;
            if(m==60)
            {
                m=0;
                h++;
                if(h==24)
                    h=0;
            }
        }
    }
    return 0;
}

//6.#从键盘输入一个年份，判断是否为闰年。
#include <stdio.h>

int main(int argc, const char *argv[])
{
    int y;
    printf("enter a year:");
    scanf("%d",&y);
    if(((y%100!=0)&&(y%4==0))||(y%400==0))
        printf("%d is a leap year.\n",y);
    else
        printf("%d is not a leap year.\n",y);
    return 0;
}

//7#编写函数将大写字母转换为小写字母
#include <stdio.h>

int main(int argc, const char *argv[])
{
    char ch;
    printf("enter a character:");
    scanf("%c",&ch);
    if((ch>=65)&&(ch<=90))
        ch=ch+32;
    printf("%c\n",ch);
    return 0;
}
//8.#验证printf函数的返回值
#include<stdio.h>
int main()

{
    int ret;
    ret=printf("hello!\n");
    printf("ret=%d\n",ret);
    return 0;
}

//9.#用printf格式化输出数据
#include <stdio.h>

int main(int argc, const char *argv[])
{
    int a=10;
    long b=100;
    float c=3.14;
    char d='A';
    unsigned int e=100;
    printf("a=%d\n",a);
    printf("b=%ld\n",b);
    printf("c=%f\n",c);
    printf("d=%c\n",d);
    printf("e=%u\n",e);
    printf("\0100\n");
    return 0;
}

//10.#输入一个数，输出其十进制数和十六进制数
#include <stdio.h>

int main(int argc, const char *argv[])
{
    int i;
    printf("enter a number:");
    scanf("%d",&i);
    printf("Decimal=%d,Hex=%#x。\n",i,i);
    return 0;
}

//11.#输入两个数，实现其加法运算
#include <stdio.h>

int main(int argc, const char *argv[])
{
    int a,b;
    printf("enter 2 numbers(by a space):");
    scanf("%d %d",&a,&b);
    printf("%d+%d=%d;\n",a,b,a+b);
    return 0;
}

//12.#观察float数输出的形式
#include <stdio.h>

int main(int argc, const char *argv[])
{
    float j=10.1;
    printf("float_j=%f\n",j);
    return 0;
}

//13.#用scanf格式化输入数据,日期以02/08/2012输入，以20120208形式输出
#include <stdio.h>

int main(int argc, const char *argv[])
{
    int y;int m;int d;
    printf("enter a date(mm/dd/yy):");
    scanf("%d/%d/%d",&m,&d,&y);
    printf("you entered the date:%04d%02d%02d\n",y,m,d);
    return 0;
}


//14.#验证getchar()与putchar(c)
#include <stdio.h>

int main(int argc, const char *argv[])
{
    char c;
    c=getchar();
    putchar(c);
    printf("\n");
    return 0;
}

//15.#验证gets(str)与puts(str)
#include <stdio.h>

int main(int argc, const char *argv[])
{
    int i;
    char str[5];
    gets(str);
    for(i=0;i<5;i++)
    {
        printf("%c",str[i]);
    }
    printf("\n");
    puts(str);
    return 0;
}

//16.#判断数据的奇偶性
#include <stdio.h>

int main(int argc, const char *argv[])
{
    int a;
    printf("enter a number(判断奇偶性):");
    scanf("%d",&a);
    (a%2)==0?printf("%d是一个偶数\n",a):printf("%d是一个奇数\n",a);
    return 0;
}

//17.#比较3个数的最大值
#include <stdio.h>

int main(int argc, const char *argv[])
{
    int x,y,z;
    printf("enter 3 numbers(以空格隔开，判断最大数):");
    scanf("%d %d %d",&x,&y,&z);
    if(x>y)
    {
        if(x>z)
            printf("%d最大\n",x);
        else
            printf("%d最大\n",z);
    }
    else
    {
        if(y>z)
            printf("%d最大\n",y);
        else
            printf("%d最大\n",z);
    }
    if(x<y)
        x=y;
    else
    {
        if(x>z)
            printf("%d最大\n",x);
        else
            printf("%d最大\n",z);
    }
    return 0;
}

//18.#判断3个数能否构成三角形
#include <stdio.h>

int main(int argc, const char *argv[])
{
    int i,j,k;
    printf("enter 3 number(以空格隔开，判断能否构成三角形):");
    scanf("%d %d %d",&i,&j,&k);
    if(i<(j+k))
    {
        (i>abs(j-k))?printf("%d %d %d能构成三角形\n",i,j,k):printf("%d %d %d构不成三角形\n",i,j,k);
    }
    else
        printf("%d %d %d构不成三角形\n",i,j,k);
    return 0;
}