《C primer plus》ch11答案
C/C++ • answer

《C primer plus》ch11答案

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/*Programming Exercise11-3*/
#include<stdio.h>
#define SIZE 20
char *getword(char *array,int len);
main()
{
    char word[SIZE];
    char *st;
    st=getword(word,SIZE-1);
    printf("%s\n",word);
}
char *getword(char *array,int len)
{
    int c;
    int i=0;
    while((c=getchar())!=' '&&c!='\n'&&c!='\t'&&i< len)
    {
        *array++=c;
        i++;
    }
    *array='\0';
    return array;
}
/*1.数组已经通过参数传递，并且修改，所以打印还是用s作为printf的一个参数*/
/*2.对于字符数组，最重要的就是结束符。在需要时一定要手动添加*/

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/*Programming Exercise11-2*/
#include<stdio.h>
#define SIZE 20
char *store(char *array,int len);
main()
{
    char s[SIZE];
    char *st;
    st=store(s,SIZE-1);
    printf("%s\n",s);
}
char *store(char *array,int len)
{
    int c;
    int i=0;
    while((c=getchar())!=' '&&c!='\n'&&c!='\t'&&i< len)
    {
        *array++=c;
        i++;
    }
    *array='\0';
    return array;
}

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/*Programming Exercise11-3*/
#include<stdio.h>
#define SIZE 20
char *getword(char *array,int len);
main()
{
    char word[SIZE];
    char *st;
    st=getword(word,SIZE-1);
    printf("%s\n",word);
}
char *getword(char *array,int len)
{
    int c;
    int i=0;
    while((c=getchar())!=' '&&c!='\n'&&c!='\t'&&i< len)
    {
        *array++=c;
        i++;
    }
    *array='\0';
    return array;
}

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/*Programming Exercise11-4*/
#include<stdio.h>
#define SIZE 20
char *search(char *array,int chr);
main()
{
    char s[SIZE];
    char *st;
    char c;
    gets(s);
    while(1)
    {
        __fpurge(stdin);
        printf("What char u wanna search?\n");
        scanf("%c",&c);
        st=search(s,c);
        if(st==NULL)
            printf("There is no %c in %s\n",c,s);
        else
            printf("%p\n",st);
    }
}
char *search(char *array,int chr)
{
    int i;
    for(i=0;array[i]!='\0';i++)
        if(array[i]==chr)
            return array+i;
    return NULL;
}
/*使用__fpurge(stdin)清空缓冲区的回车*/

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/*Programming Exercise11-5*/
#include<stdio.h>
int is_within(char c,char *str);
main()
{
    char s[100];
    char c;
    printf("Please input the string\n");
    gets(s);
    while(1)
    {
        printf("what char u wanna search?\n");
        __fpurge(stdin);
        c=getchar();
        if(is_within(c,s))
            printf("IN\n");
        else
            printf("NOT IN\n");
    }
}
int is_within(char c,char *str)
{
    int i;
    while(*str!=c||*str!=EOF)
        str++;
    return *str;
 
}
/*使用__fpurge(stdin)清空缓冲区的回车*/

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/*Programming Exercise11-6*/
#include<stdio.h>
char *Strncpy(char *s1,char *s2,int n);
main()
{
    char s1[100],s2[100];
    int n;
    gets(s2);
    printf("Please input n:\n");
    scanf("%d",&n);
    Strncpy(s1,s2,n);
    puts(s1);
}
char *Strncpy(char *s1,char *s2,int n)
{
    int i=0;
    for(i=0;i < n;i++)
        s1[i]=s2[i];
    s1[i]='\0';
 
}

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/*Programming Exercise11-7*/
#include<stdio.h>
#include<string.h>
char *string_in(const char *s1,const char *s2);
main()
{
    char *ptr;
    ptr=string_in("transportation","transportation");
    if(ptr)
        puts(ptr);
    else
        puts("Not found");
}
char *string_in(const char *s1,const char *s2)
{
    int len1,len2;
    int no=1;
    int times;
    len2=strlen(s2);
    len1=strlen(s1);
    times=len1-len2+1;
    printf("%d %d\n",len1,len2);
    if(times>0)
        while(no=strncmp(s1,s2,len2)&&times--)
            s1++;
    if(no)
        return NULL;
    else
        return (char *) s1;
}
/*1.比较的次数自然要加1，否则当s1就是s2的时候会出现找不到*/
/*2.对s1进行自增运算，strncmp中的s1也就发生了变化*/

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/*Programming Exercise11-8*/
#include<stdio.h>
#include<string.h>
void rev_string(char *s);
main()
{
    char a[100];
    gets(a);
    rev_string(a);
    puts(a);
}
void rev_string(char *s)
{
    int i=0;
    int len,temp;
    len=strlen(s);
    for(i=0;i < len/2;i++)
    {
        temp=s[i];
        s[i]=s[len-1-i];
        s[len-1-i]=temp;
    }
}
/*1.不需要使用两个数组，一个数组就可以，也不需要指针*/
/*2.注意i<len/2，因为只需要把首尾对称的元素调换即可*/

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/*Programming Exercise11-9*/
#include<stdio.h>
#include<string.h>
void no_space(char *s);
main()
{
    char a[100];
    gets(a);
    no_space(a);
    //puts(a);
}
void no_space(char *s)
{
    int i;
    int len;
    char *pos;
    char *start=s;
    while(*s)
    {
        if(*s==' ')
        {
            pos=s;
            do
            {
                *pos=*(pos+1);
                pos++;
            }while(*pos);
            //printf("移动后结果：%s\n",start);
        }
        else
            s++;
    }
}
/*1.当有空格的时候，需要用后面的字符串覆盖前面字符串*/
/*2.当遇到空格时候，用新的指针pos指向当前位置，然后不断用后面字符覆盖前面*/
/*3.while(*pos)表明了，当遇到空格，后面覆盖前面是到字符串最终结尾为止的*/
/*4.相当于空格后面的字符串整体前移*/

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/*Programming Exercise11-10*/
#include<stdio.h>
#include<string.h>
#define MAXLINES 10
#define MAXLEN 100
#define ALLOCSIZE 1000
int Readlines(char *lineptr[],int nlines);
void Writelines(char *lineptr[],int nlines);
void qsort(void *v[],int left,int right,int (*comp)(void *,void *));
void as_order(char *lineptr[],int lines);
void s2l_order(char *lineptr[],int lines);
void word_order(char *lineptr[],int lines);
main()
{
    char *list[MAXLINES];
    int flag=1;
    int n,lines;
    printf("----------------------------------------------\n\n");
    printf(" * Please input 10 strings\n");
    while((lines=Readlines(list,MAXLINES))<=0)//括号要有，赋值优先级低
        printf("Please input 10 strings\n");
    printf("\n* Input succeed!\n");
    printf("* U have input %d lines\n",lines);
    printf("\n----------------------------------------------\n");
    printf("1.按初始顺序输出\t2.按ASCII顺序输出\n");
    printf("3.按长度递增顺序输出\t4.按首单词长度顺序输出\n");
    printf("q.退出\n");
    printf("----------------------------------------------\n");
    __fpurge(stdin);
    printf("PLease chose ur function\n");
    flag=scanf("%d",&n);
    while(flag==1)
    {
        switch(n)
        {
            case 1:
                printf("按初始顺序输出:\n");
                Writelines(list,lines);
                break;
            case 2:
                printf("按ASCII顺序输出:\n");
                as_order(list,lines);
                break;
            case 3:
                printf("按长度递增顺序输出:\n");
                s2l_order(list,lines);
                break;
            case 4:
                printf("按首单词长度顺序输出:\n");
                word_order(list,lines);
                break;
            default:
                printf("\nError:You should choose from the table!\n");
                break;
        }
        printf("----------------------------------------------\n");
        printf("PLease chose ur function\n");
        flag=scanf("%d",&n);
    }
}
 
int Getline(char line[],int maxline);//读入字符串函数
char *alloc(int);//储存空间分配函数
int Readlines(char *lineptr[],int maxlines)
{
    int len;
    int nlines;
    char *p;//永久储存空间的字符串指针
    char line[MAXLEN];
    nlines=0;
    while((len=Getline(line,MAXLEN))>0)
        if(nlines>=maxlines||(p=alloc(len))==NULL)
            return -1;//不做小于10行的判断，只规定不能超过10行
        else
        {
            line[len-1]='\0';   //删除换行符
            strcpy(p,line);     //把临时空间line中字符串复制到永久空间
            lineptr[nlines++]=p;//储存指针地址
        }
    return nlines;//允许小于10行的任意行输出
 
}
int Getline(char s[],int lim)
{
    int c,i;
    for(i=0;i<(lim-1)&&(c=getchar())!=EOF&&c!='\n';i++)
        s[i]=c;
    if(c=='\n')
    {
        s[i]=c;
        ++i;
    }
    s[i]='\0';
    return i;
}
void Writelines(char *lineptr[],int nlines)
{
    while(nlines-->0)
    {
        printf("%s\n",*lineptr++);
    }
 
}
static char allocbuf[ALLOCSIZE];//永久储存空间
static char *allocp=allocbuf;
char *alloc(int n)
{
    if(allocbuf+ALLOCSIZE-allocp>=n)
    {
        allocp+=n;
        return allocp-n;
    }
    else
        return 0;
}
void qsort(void *v[],int left,int right,int (*comp)(void *,void *))
{
    int i,last;
    void swap(void *v[],int i,int j);
    if(left>=right)
        return ;
    swap(v,left,(left+right)/2);
    last=left;
    for(i=left+1;i<=right;i++)
        if((*comp)(v[i],v[left])<0)
            swap(v,++last,i);
    swap(v,left,last);
    qsort(v,left,last-1,comp);
    qsort(v,last+1,right,comp);
}
int lencmp(char v1[],char v2[])
{
    int len1,len2;
    len1=strlen(v1);
    len2=strlen(v2);
    if(len1>len2)
        return 1;
    else if(len1< len2)
        return -1;
    else
        return 0;
}
int wordcmp(char v1[],char v2[])
{
    int i,j;
    i=j=0;
    while(v1[i]!=' ')
        i++;
    while(v2[j]!=' ')
        j++;
    if(i>j)
        return 1;
    else if(i< j)
        return -1;
    else
        return 0;
}
void swap(void *v[],int i,int j)
{
    void *temp;
    temp=v[i];
    v[i]=v[j];
    v[j]=temp;
}
void s2l_order(char *lineptr[],int lines)
{
    qsort((void **)lineptr,0,lines-1,(int (*)(void *,void *))(lencmp));
    Writelines(lineptr,lines);
}
void word_order(char *lineptr[],int lines)
{
    qsort((void **)lineptr,0,lines-1,(int (*)(void *,void *))(wordcmp));
    Writelines(lineptr,lines);
}
void as_order(char *lineptr[],int lines)
{
    qsort((void **)lineptr,0,lines-1,(int (*)(void *,void *))(strcmp));
    Writelines(lineptr,lines);
}

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/*Programming Exercise11-11*/
#include<stdio.h>
#include<ctype.h>
int word_count(char *s);
int upper_count(char *s);
int lower_count(char *s);
int punct_count(char *s);
int digit_count(char *s);
int isword(char *s);
#define SIZE 100
main()
{
    int c;
    char s[SIZE];
    int i=0;
    int nword,nupper,nlower,npunct,ndigit;
    nword=nupper=nlower=npunct=ndigit=0;
    printf("Please input a string\n");
    while((c=getchar())!=EOF&&c!='\n')
    {
        s[i]=c;
        i++;
    }
    s[i]='\0';
    printf("输入的字符串：%s\n",s);
    nword=word_count(s);
    nupper=upper_count(s);
    nlower=lower_count(s);
    npunct=punct_count(s);
    ndigit=digit_count(s);
    printf("words:%d\n",nword);
    printf("upper-case:%d\n",nupper);
    printf("lower-case:%d\n",nlower);
    printf("punctuation:%d\n",npunct);
    printf("digit:%d\n",ndigit);
}
#define OUT 0
#define IN 1
int word_count(char *s)
{
    int i=0;
    int count=0;
    int state=OUT;
    while(s[i]!='\0'&&s[i]==' ')
        i++;
    while(s[i]!='\0')
    {
        if((ispunct(s[i])&&s[i]!='-')||isblank(s[i])||s[i]=='\n')
            state=OUT;
        else if(state==OUT&&!isdigit(s[i]))
        {
            state=IN;
            count++;
        }
        i++;
    }
    return count;
}
int upper_count(char *s)
{
    int i=0;
    int count=0;
    while(s[i]!='\0')
    {
        if(isupper(s[i]))
            count++;
        i++;
    }
    return count;
}
int lower_count(char *s)
{
    int i=0;
    int count=0;
    while(s[i]!='\0')
    {
        if(islower(s[i]))
            count++;
        i++;
    }
    return count;
}
int punct_count(char *s)
{
    int i=0;
    int count=0;
    while(s[i]!='\0')
    {
        if(ispunct(s[i]))
            count++;
        i++;
    }
    return count;
}
int digit_count(char *s)
{
    int i=0;
    int count=0;
    while(s[i]!='\0')
    {
        if(isdigit(s[i]))
            count++;
        i++;
    }
    return count;
}

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/*Programming Exercise11-12*/
#include<stdio.h>
int main(int argc,char *argv[])
{
    int i=argc;
    while(i-->1)
        argv++;//首先把指针移动到倒数第二个位置
    while(argc-->1)
        printf("%s ",*argv--);//逆序打印但是不能打印argv[0]
    printf("\n");
}

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/*Programming Exercise11-13*/
#include<stdio.h>
#include<stdlib.h>
int main(int argc,char *argv[])
{
    double base,power,temp=1,result=1;//必须有初值
    base=atof(argv[1]);
    power=atof(argv[2]);
    if(power==0)
        result=1;
    else if(power<0)
    {
        power=-power;//为了递减，需要变成正数
        while(power-->0)
            temp*=base;
        result=1/temp;
    }
    else
        while(power-->0)
            result*=base;
    printf("%.3f^%.3f=%.3f\n",base,power,result);
}

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/*Programming Exercise11-14*/
#include<stdio.h>
#include<ctype.h>
#define SIZE 100
int myatoi(char *s);
main()
{
    int num,c,i=0;
    char s[SIZE];
    printf("Please input a string\n");
    while((c=getchar())!='\n')
    {
        s[i]=c;
        i++;
    }
    s[i]='\0';
    printf("the int number: \n");
    if(num=myatoi(s))
        printf("%d\n",num);
    else
        printf("the string is not a int number!\n");
}
int myatoi(char *s)
{
    int sign=1;
    int i=0;
    int n=0;
    if(s[i]=='-')
    {
        sign=-1;
        i++;//只有当s[0]是负号的时候才跳过
    }
    else
        sign=1;//否则仍让从s[0]开始
    while(s[i]!='\0')
    {
        if(isdigit(s[i]))
        {
            n=n*10+s[i]-'0';
        }
        else
            return 0;
        i++;
    }
    return n*sign;
}

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/*Programming Exercise11-15*/
#include<stdio.h>
#include<ctype.h>
#define SIZE 1000
int main(int argc,char *argv[])
{
    int c,i=0;
    char s[SIZE];
    char *p;
    while((c=getchar())!=EOF)
    {
        s[i]=c;
        i++;
    }
    s[i]='\0';
    p=s;
    //printf("%c %c\n",*argv[1],*(argv[1]+1));
    if(argc>1&&*argv[1]=='-')
    {
        if(*(argv[1]+1)=='p')
        {
            printf("按照原样输出：\n");
            while(*p!='\0')
                putchar(*p++); 
        }
        else if(*(argv[1]+1)=='u')
        {
            printf("全部转换为大写字母：\n");
            while(*p!='\0')
                putchar(toupper(*p++));
        }
        else if(*(argv[1]+1)=='l')
        {
            printf("全部转换为大写字母：\n");
            while(*p!='\0')
                putchar(tolower(*p++));
        }
        else
            printf("Only -p,-l,-u please!\n");
    }
    else
        printf("请输入命令行参数-p,-l,-u\n");
}

本文采用中国大陆版CC协议发布
作者保留以下权利：

  1. 署名（Attribution）：必须提到原作者。
  2. 非商业用途（Noncommercial）：不得用于盈利性目的。
  3. 禁止演绎（No Derivative Works）：不得修改原作品, 不得再创作。
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