c primer plus(五版)编程练习-第七章编程练习

1．编写一个程序。该程序读取输入直到遇到#字符，然后报告读取的空格数目、读取的换行符数目以及读取的所有其他字符数目。

#include<stdio.h>
#include<ctype.h>
int main(void){
    char ch;
    int count1,count2,count3;
    count1 = count2 = count3 = 0; 　　printf("Enter text to be analyzed(#to terminate)：\n");
    while((ch = getchar()) != ‘#‘){
        if ( ch == ‘\n‘){
            count1++;
        } else if(isspace(ch)){
            count2++;
        } else if (!isspace(ch)){
            count3++;
        }
    }
    printf("换行数量%d,空格数量%d,其他字符数量%d",count1,count2,count3);
    return 0;
}

2．编写一个程序。该程序读取输入直到遇到#字符。使程序打印每个输入的字符以及它的十进制ASCII 码。每行打印8 个字符/编码对。建议：利用字符计数和模运算符(%)在每8 个循环周期时打印一个换行符。

#include<stdio.h>
#define STOP ‘#‘
int main(void){
    char ch;
    int length = 1;
    printf("Enter text to be analyzed(#to terminate)：\n");
    while((ch = getchar()) != STOP){
        if(length%8==0){
            printf("\n");
        }
        printf("%c/%d ",ch,ch);
        length++;
    }
    return 0;
}

3．编写一个程序。该程序读取整数，直到输入0。输入终止后，程序应该报告输入的偶数(不包括0)总个数、偶数的平均值，输入的奇数总个数以及奇数的平均值。

#include<stdio.h>
int main(void){
    int num,even_num,odd_num;
    double even_count,odd_count;//必需定义为double类型,否则打印平均值会出错
    even_num = odd_num = 0;
    even_count = odd_count = 0.0 ;
    printf("Enter int to be analyzed(0 to terminate)：\n");
    while (scanf("%d", &num) == 1 && num != 0){
            if (num%2 == 0){
                even_num++;
                even_count +=num;
            } else {
                odd_num++;
                odd_count +=num;
            }
    }
    if (even_count > 0)
        printf("Even have %d, even average is %.2f\n",even_num,even_count / even_num);
    if (odd_num > 0)
        printf("Odd have %d,odd average is %.2f",odd_num,odd_count/odd_num);
    return 0;
}

4．利用if else 语句编写程序读取输入，直到#。用一个感叹号代替每个句号，将原有的每个感叹号用两个感叹号代替，最后报告进行了多少次替代。

#include<stdio.h>
#define STOP ‘#‘
int main(void){
    char ch;
    int i;
    i = 0;
    while((ch = getchar()) != STOP){
        if (ch == ‘.‘){
            putchar(‘!‘);
            i++;
        } else if (ch == ‘!‘){
            putchar(ch);
            putchar(ch);
            i++;
        } else {
            putchar(ch);
        }
    }
    printf("\n");
    printf("count %d",i);
    return 0;
}

5．用switch 重做练习3。

#include<stdio.h>
int main(void){
    int num,even_num,odd_num;
    double even_count,odd_count;//必需定义为double类型,否则打印平均值会出错
    even_num = odd_num = 0;
    even_count = odd_count = 0.0 ;
    printf("Enter int to be analyzed(0 to terminate)：\n");
    while (scanf("%d", &num) == 1 && num != 0){
            switch (num%2){
                case 0:
                    even_num++;
                    even_count +=num;
                    break;
                case 1:
                    odd_num++;
                    odd_count +=num;
                    break;
            }
    }
    if (even_count > 0)
        printf("Even have %d, even average is %.2f\n",even_num,even_count / even_num);
    if (odd_num > 0)
        printf("Odd have %d,odd average is %.2f",odd_num,odd_count/odd_num);
    return 0;
}