第二章：分支结构

/*简单的猜数游戏*/
#include
int main(void)
{int mynumber&＃61;38;int yournumber;printf("Input your number:");scanf("%d",&yournumber);if(yournumber&＃61;mynumber)printf("Ok!you are right!\n");elseif(yournumber>mynumber)printf("Sorry!your number is bigger than my number!\n");elseprintf("Sorry!your number is smaller than my number!\n");return 0;
}

/*判断是奇数还是偶数*/
#include
int main(void)
{int number;printf("Enter a number:");scanf("%d",&number);if(number%2&＃61;&＃61;0){printf("The number is even.\n");}else{printf("The number is odd.\n");}return 0;
}

/* 输入一批学生的成绩&＃xff0c;计算平均分&＃xff0c;并统计不及格成绩的学生人数*/
#include
int main(void)
{int count,i,n;double grade,total;printf("Enter n:");scanf("%d",&n);total&＃61;0;count&＃61;0;for(i&＃61;1;i<&＃61;n;i&＃43;&＃43;){printf("Enter grade#%d:",i);scanf("%lf",&grade);total&＃61;total&＃43;grade;if(grade<60){count&＃43;&＃43;;}}printf("Grade average&＃61;%.2f\n",total/n);printf("Number of failures&＃61;%d\n",count);return 0;
}

/*计算多分段函数*/
#include
int main(void)
{double x,y;printf("Enter x:");scanf("%lf",&x);if(x<0){y&＃61;0;}else if(x<&＃61;15){y&＃61;4*x/3;}else{y&＃61;2.5*x-10.5;}printf("f(%.2f)&＃61;%.2f\n",x,y);return 0;
}

/*求解简单的四则运算*/
#include
int main(void)
{double value1,value2;char op;printf("Type in an expression:");scanf("%lf%c%lf",&value1,&op,&value2);if(op&＃61;&＃61;&＃39;&＃43;&＃39;)printf("&＃61;%.2f\n",value1&＃43;value2);else if(op&＃61;&＃61;&＃39;-&＃39;)printf("&＃61;%.2f\n",value1-value2);else if(op&＃61;&＃61;&＃39;/&＃39;)printf("%.2f\n",value1/value2);elseprintf("Unknown operator\n");return 0;
}

/* 统计字符&＃xff0c;包括英文字母、数字字母和其他字母的个数 */
#include
int main(void)
{int digit,letter,other;char ch;int i;digit&＃61;letter&＃61;other&＃61;0;printf("Enter 10 characters:");for(i&＃61;1;i<&＃61;10;i&＃43;&＃43;){ch&＃61;getchar();if(ch>&＃61;&＃39;a&＃39;&& ch<&＃61;&＃39;z&＃39;)//(ch>&＃61;&＃39;A&＃39;&& ch<&＃61;&＃39;Z&＃39;))letter&＃43;&＃43;;else if(ch>&＃61;&＃39;0&＃39;&& ch<&＃61;&＃39;9&＃39;)digit&＃43;&＃43;;elseother&＃43;&＃43;;}printf("letter&＃61;%d,digit&＃61;%d,other&＃61;%d\n",letter,digit,other);return 0;
}

/* 查询自动售货机中商品的价格 */
#include
int main(void)
{int choice,i;double price;for(i&＃61;1;i<&＃61;5;i&＃43;&＃43;){printf("[1]Select crisps\n");printf("[2]Select popcorn\n");printf("[3]Select chocolate\n");printf("[4]Select cola\n");printf("[0]exit\n");printf("Enter choice:");scanf("%d",&choice);if(choice&＃61;&＃61;0)break;switch(choice){case1:price&＃61;3.0;break;case2:price&＃61;2.5;break;case3:price&＃61;4.0;break;case4:price&＃61;3.5;break;default:price&＃61;0.0;break;}}printf("Thanks\n");return 0;
}

/*求解简单的四则运算表达式*/
#include
int main(void)
{double value1,value2;char op;printf("Type in an expression:");scanf("%lf%c%lf",&value1,&op,&value2);switch(op){case&＃39;&＃43;&＃39;:printf("&＃61;%.2f\n",value1&＃43;value2);break;case&＃39;-&＃39;:printf("&＃61;%.2f\n",value1-value2);break;case&＃39;*&＃39;:printf("&＃61;%.2f\n",value1*value2);case&＃39;/&＃39;:printf("&＃61;%.2f\n",value1/value2);break;default:printf("Unknown operator\n");break;}return 0;
}

/* 统计字符&＃xff0c;包括空格或回车、数字字符和其他字符的个数 */
#include
int main(void)
{int blank,digit,other;char ch;int i;blank&＃61;digit&＃61;other&＃61;0;printf("Enter 10 characters:");for(i&＃61;1;i<&＃61;10;i&＃43;&＃43;){ch&＃61;getchar();switch(ch){case&＃39; &＃39;:case&＃39;\n&＃39;:blank&＃43;&＃43;;break;case&＃39;0&＃39;: case&＃39;1&＃39;: case&＃39;2&＃39;: case&＃39;3&＃39;: case&＃39;4&＃39;:case&＃39;5&＃39;: case&＃39;6&＃39;: case&＃39;7&＃39;: case&＃39;8&＃39;: case&＃39;9&＃39;:digit&＃43;&＃43;;break;default:other&＃43;&＃43;;break;}}printf("blank&＃61;%d,digit&＃61;%d,other&＃61;%d\n",blank,blank,digit,other);return 0;
}

/*求解简单的四则运算表达式*/
#include
int main(void)
{double value1,value2;char op;printf("Type in an expression:");scanf("%lf%c%lf",&value1,&op,&value2);if(op&＃61;&＃61;&＃39;&＃43;&＃39;)printf("&＃61;%.2f\n",value1&＃43;value2);else if(op&＃61;&＃61;&＃39;-&＃39;)printf("%.2f\n",value1-value2);else if(op&＃61;&＃61;&＃39;*&＃39;)printf("&＃61;%.2f\n",value1*value2);else if(op&＃61;&＃61;&＃39;/&＃39;)if(value2!&＃61;0)printf("&＃61;%.2f\n",value1/value2);elseprintf("Divisor can not be 0!\n");elseprintf("Unknown operator!\n");return 0;
}