C Primer Plus 第8章 字符输入/输出和验证输入 编程练习

1.
#include <stdio.h>
int main(){
    char ch;
    int ct = 0;
    while ((ch=getchar()) != EOF)
        ct++;
    printf("%d characters read.", ct);
    return 0;
}

2.
#include <stdio.h>
int main(){
    char ch;
    int ct = 0;
    while ((ch = getchar()) != EOF)
    {
        if (ch >= 32){
            putchar(ch);
            printf("/%d  ",ch);
            ct++;
        }
        else if (ch == '\n'){
            printf("\\n");
            putchar(ch);
            ct = 0;  //因为要换新的一行了所以ct清0
        }
        else if (ch == '\t'){

            printf("\\t");
            ct++;
        }
        else  //打印控制字符
        {
            putchar('^');
            putchar(ch + 64);
            printf("/%d  ", ch);
        }
        if (ct == 10){
            printf("\n");
            ct = 0;
        }
    }
    return 0;
}

3.
#include <stdio.h>
#include <ctype.h>
int main(){
    char ch;
    int a,b,c;
    a = b = c = 0;
    while ((ch = getchar()) != '#')
    {
        if (isupper(ch))
            a++;
        else if (islower(ch))
            b++;
        else c++;
    }
    printf("capital:%d lower case:%d other:%d", a, b, c);
    return 0;
}

4.
#include <stdio.h>
#include <ctype.h> //用来区分字母和字母的大小写
#include <stdbool.h>
int main(){
    char ch;
    bool inword = false;
    int n_chars = 0;
    int n_words = 0;
    int value;
    while ((ch = getchar()) != '#')
    {
        if (isalpha(ch))
            n_chars++;
        if (!isspace(ch) && !inword)
        {
            inword = true; //开始一个新的单词
            n_words++; //单词加1
        }
        if (isspace(ch) && inword)
            inword = false; //单词结束
    }
    value = n_chars / n_words ;
    printf("chars : %d\n", n_chars);
    printf("words : %d\n", n_words);
    printf("average value : %d", value);
    return 0;
}

5.
#include <stdio.h>
//如果50太大，则50变为最大值。反之则为最小值。
int main(){
    char ch;
    int guess = 50, MAX = 100, MIN = 0;
    printf("Uh...is your number is %d\n",guess);
    while ((ch = getchar()) != 'y')
    {
        if (ch == 'b') {
            MAX = guess;
            guess = (guess + MIN) / 2;
            printf("Well, then, is it %d\n",guess);
        }
        else if (ch == 'l') {
            MIN = guess;
            guess = (guess + MAX) / 2;
            printf("Well, then, is it %d\n",guess);
        }
        else printf("Sorry, I understand only big , less , yes.\n");
        while ((ch = getchar()) != '\n')
            continue;
    }
    printf("I konw i could do it");
    return 0;
}

6.
//重要！！
char get_first(void){
    char ch;
    while((ch = getchar()) == '\n')
        continue;
    while (getchar() != '\n')
        continue;
    return ch;
}

7.
#include <stdio.h>
char get_choice(void);
char get_first(void);
#define WORK_OVERTIME 40
#define RATE1 0.15
#define RATE2 0.20
#define RATE3 0.25
#define BREAK1 300.0
#define BREAK2 450.0
#define BASE1 (BREAK1 * RATE1)
#define BASE2 (BASE1 + ((BREAK2 - BREAK1) * RATE2))
int main(void) {
    int hr;
    char choice;
    double wage,income,tax,wage2;
    printf("------------------------------------------------------------------------\n");
    printf("Enter the number number corresponding to the desired pay rate or action:\n");
    printf("a) $8.15/hr                       b) $9.33/hr\n");
    printf("c) $10.00/hr                      d) $11.20/hr\n");
    printf("q) quit\n");
    printf("------------------------------------------------------------------------\n");
    printf("Please enter your choise:");
    while (choice = get_choice() ){
        if (choice == 'q')
            break;
        switch (choice){
            case 'a': wage2 = 8.75;
                break;
            case 'b': wage2 = 9.33;
                break;
            case 'c': wage2 = 10.00;
                break;
            case 'd': wage2 = 11.20;
                break;
        }
        printf("Please enter the hours:");
        scanf("%d",&hr);
        if (hr <= WORK_OVERTIME)
            wage = hr * wage2;
        else wage = WORK_OVERTIME * wage2 +((hr - WORK_OVERTIME) * wage2 * 1.5);
        if (wage <= BREAK1){
            tax = wage * RATE1;
        }
        else if (wage > 300 && wage <= 450 ){
            tax = BASE1 + (wage - BREAK1) * RATE2;
        }
        else tax = BASE2 + (wage - BREAK2) * RATE3;
        income = wage - tax;
        printf("The wage: %.2f income:%.2lf tax:%.2lf\n", wage, income, tax);
        printf("------------------------------------------------------------------------\n");
        printf("Enter the number number corresponding to the desired pay rate or action:\n");
        printf("1) $8.15/hr                       2) $9.33/hr\n");
        printf("3) $10.00/hr                      4) $11.20/hr\n");
        printf("5) quit\n");
        printf("------------------------------------------------------------------------\n");
        printf("Please enter your choise:");
    }
    return 0;
}
//get_choice 输入正确的符号
char get_choice(void){
    char ch;
    ch = get_first();
    while (ch != 'q' && (ch < 'a' || ch > 'd')){
        printf("Please enter the : a b c d q\n");
        printf("Please enter your choise:");
        ch = get_first();
    }
    return  ch;
}
//get_first 读取第一个符号 扔掉其他符号
char get_first(void){
    int ch;
    ch = getchar();
    while (getchar() != '\n')
        continue;
    return ch;
}

8.
#include <stdio.h>

char get_choice(void);
char get_first(void);
double get_number(void);

int main(void){
    char choice;
    double num1,num2,result;

    while ((choice = get_choice()) != 'q'){
        printf("Enter the first number:");
        num1 = get_number();
        printf("Enter the second number:");
        num2 = get_number();
        if (choice == 'a') {
            result = num1 + num2;
            printf("%.1lf + %.1lf = %.1lf\n", num1, num2, result);
        }
        if (choice == 's') {
            result = num1 - num2;
            printf("%.1f - %.1f = %.1f\n", num1, num2, result);
        }
        if (choice == 'm') {
            result = num1 * num2;
            printf("%.1f * %.1f = %.1f\n", num1, num2, result);
        }
        if (choice == 'd') {
            if (num2 == 0) {
                printf("Enter a number other than 0: ");
                num2 = get_number();
                result = num1 / num2;
                printf("%.1f / %.1f = %.1f\n",  num1, num2, result);
            } else
                printf("%.1f / %.1f = %.1f\n", num1, num2, result);
        }
    }

    return 0;
}

char get_choice(void){
    char ch;
    printf("Enter the operation of your choice:\n");
    printf("a. add            s. subtract\n");
    printf("m. multiply       d. divide\n");
    printf("q. quit\n");
    ch = get_first();
    while ((ch != 'a') && (ch != 's') && (ch != 'm') && (ch != 'd') && (ch != 'q')){
        printf("Please choice such as a s m d q:");
        ch = get_first();
    }
    return ch;
}

char get_first(void){
    char ch;
    while((ch = getchar()) == '\n')//ch = getchar();之前用的的是这个，结果总是把回车给ch
        continue;    //还总是检查不出来问题，终于找出来问题在哪里了。！！
    while (getchar() != '\n')
        continue;
    return ch;
}

double get_number(void){
    double num;
    char ch;
    while (scanf("%lf", &num) != 1){
        while ((ch = getchar()) != '\n')
            putchar(ch); //处理错误的输入。
        printf("is not an number.\n");
        printf("Please enter a number , such as 2.5, -1.78E8, or 3:");
    }
    return num;
}