【C语言学习】《C Primer Plus》第7章 C控制语句：分支与跳转

 

学习总结

 

1、if…else…从语义上看就能出用途，跟其他语言没差多少，只需要记住，世界上最遥远的距离之一：我走if你却走else。

 

2、根据个人几年的编程经验，太多的if…else…嵌套会加大代码的可读性和维护难度。个人认为代码最好不要超过三层if…else…的嵌套，否则最好使用布尔值控制流程。

 

3、逻辑运算符优先级：!>&&>||

 

4、运行到continue语句将导致剩余的迭代部分被忽略，开始下一次迭代。continue仅用于循环，而break语句用于循环和switch中。

 

5、编程题（题1）：

#include <stdio.h>

int main(){
        int space=0,newline=0,other=0;
        char ch;
        printf("please enter something:
");
        while((ch=getchar())!='#'){
                if(ch=='
'){
                        newline+=1;
                }else if(ch==' '){
                        space+=1;
                }else{
                        other+=1;
                }
        }
        printf("space is %d
",space);
        printf("newline is %d
",newline);
        printf("other is %d
",other);
        return 0;
}

运行结果：

please enter something:

hello world!

hi nihao.

#ABC

space is 2

newline is 2

other is 19

6、编程题（题11）：

#include <stdio.h>
#define ARTICHOKE_UNIT_PRIC 1.25
#define BEET_UNIT_PRICE 0.65
#define CAROTA_UNIT_PRICE 0.89
#define DISCOUNT 0.05 
#define T_0_5 3.50
#define T_5_20 10.00
#define T_20_ 0.1

int main(){
        double a,b,c,ap,bp,cp,ac,bc,cc,sc,dc,tc;
        ap=ARTICHOKE_UNIT_PRIC;
        bp=BEET_UNIT_PRICE; 
        cp=CAROTA_UNIT_PRICE;  
        printf("how many artichoke you want(pound):");
        scanf("%lf",&a);
        if(a==0)return 0;

        printf("how many beet you want(pound):");
        scanf("%lf",&b);
        if(b==0)return 0;

        printf("how many carota you want(pound):");
        scanf("%lf",&c);
        if(c==0)return 0;

        printf("
------UNIT PRICE------
");
        printf("artichoke's unit price is $%.2f(one pound) 
",ap);
        printf("beet's unit price is $%.2f(one pound)
",bp);
        printf("carota'unit price is $%.2f(one pound)
",cp);

        printf("
------ORDER------
");
        printf("artichoke:%.2fpound
",a);
        printf("beet:%.2fpound
",b);
        printf("carota:%.2fpound
",c);

        printf("
artichoke is $%.2f",a*ap);
        printf("
beet is $%.2f",b*bp);
        printf("
carota is $%.2f
",c*cp);
        sc=a*ap+b*bp+c*cp;
        printf("
total cost is $%.2f",sc);
        dc=sc>100?sc*DISCOUNT:0;
        printf("
discount is $%.2f",dc);

        printf("
total weight is %.2f",a+b+c);
        if(0<(a+b+c)<=5){
                tc=T_0_5;
        }
        if(5<(a+b+c) && (a+b+c)<=20){
                tc=T_5_20;
        }
        if((a+b+c)>20){
                tc=8+(a+b+c)*0.1;
        }
        printf("
ttransport cost is $%.2f",tc);
        printf("
order cost is $%.2f
",sc-dc+tc);

        return 0;
}

运行结果：

how many artichoke you want(pound):123

how many beet you want(pound):234

how many carota you want(pound):343

 

------UNIT PRICE------

artichoke's unit price is $1.25(one pound)

beet's unit price is $0.65(one pound)

carota'unit price is $0.89(one pound)

 

------ORDER------

artichoke:123.00pound

beet:234.00pound

carota:343.00pound

 

artichoke is $153.75

beet is $152.10

carota is $305.27

 

total cost is $611.12

discount is $30.56

total weight is 700.00

ttransport cost is $78.00

order cost is $658.56