C_控制语句

1.字符输入 and 输出

变量 = getchar()
putchar(变量)

    char a;
    a = getchar();
    putchar(a);

2.顺序结构

#include<stdio.h>
main()
{
    int i ,a,b,c;
    scanf("%d",&i);
    a = i%10;//求个位数
    b = (i/10)%10;
    c = i /100;
    printf("%d
%d
%d
",a, b, c);
}

3.选择结构

#include<stdio.h>
main()
{
    int a, b,max;
    scanf("%d%d",&a,&b);
    if (a>=b)
    {
        max = a;
    }
    else
    {
        max = b;
    }
    printf("%d
",max);
    return 0;
}

4.三元运算符

表达式1 ? 表达式2 ：表达式3

5.综合运用（求方程的根）

#include<stdio.h>
#include<math.h>
#include<stdlib.h>//调用exit()函数时要有
#define EPS 1e-6
main()
{
    float a, b, c,disc, p, q;
    printf("Please enter a, b, c:");
    scanf("%f,%f,%f",&a,&b, &c);
    if (fabs(a) <= EPS)
    {
        printf("It is not a quadratic equation !
");
        exit(0);//退出程序    
    }

    disc = b*b - 4* a *c;
    p = -b /(2 *a);
    q = sqrt(fabs(disc))/(2 *a);
    if (fabs(disc) <= EPS)
    {
        printf("Two equal real roots: x1 = x2 = %6.2f
",p);
    }
    else if(disc > EPS)
    {
        printf("Two unequal real roots: x1 =%6.2f,x2 =%6.2f
",p + q, p-q);
    }
    else
    {
        printf("Two complex roots:
");
        printf("x1 = %6.2f + %6.2fi
",p,q);
        printf("x2 = %6.2f - %6.2fi
",p,q);
    }
}

6.猜数字

#include<stdlib.h>
#include<stdio.h>
main()
{
    int magic;
    int guess;
    magic = rand();
    printf("Please guess a magic number:");
    scanf("%d",&guess);
    if (guess > magic)
    {
        printf("Wrong! Too high !
");
    }
    else if (guess == magic)
    {
        printf("Right !
");
    }
    else
    {
        printf("Wrong ! Too low !
");
    }
    printf("The magic number is :%d
",magic);
}

7.开关语句

switch (n):
{
    case 1:
    case 2:
    case 3:
}

8.循环语句

#include<stdlib.h>
#include<stdio.h>
main()
{
    while()
    {
        
    }

    do 
    {
    
    }while();

    for(  ;  ;  )
    {
    
    }

}

9.循环实例

#include<stdlib.h>
#include<stdio.h>
main()
{
    int magic;
    int guess;
    int i = 1;
    magic = rand()%100+1;#1到100之间的随机数
    printf("Please guess a magic number:");
    scanf("%d",&guess);
    for(i; i<= 100000;i++)
    {
    if (guess > magic)
    {
        printf("Wrong! Too high !
");
    }
    else if (guess == magic)
    {
        printf("Right !
");
        break;
    }
    else
    {
        printf("Wrong ! Too low !
");
    }
    scanf("%d",&guess);
    
    }
    printf("The magic number is :%d
",magic);
    printf("%d
",i);
}

10.嵌套循环实例

11.流程控制语句

　　break

　　continue