C Primer Plus（第六版）第十一章 编程练习答案

Posted 2021-09-26 水番正文

前言：这次感觉融起来了，各章的知识都有用到，不过这次时间隔的是够久的。

仅供参考，新手勿喷。

CH11 Code answer 1:

#include <stdio.h>

#define SIZE 100
void s_gots(char *);

int main(void)
{
	char str[SIZE];
	
	printf("Enter your string(enter q to quit):"); 
	s_gots(str);
	printf("REVIEW:%s",str);
	
	return 0;
} 

void s_gots(char * str)
{
//	char str[SIZE];						这是局部变量的地址 当用这个地址返回 这个函数的栈帧已经被销毁
//										虽然数据可能还在 但行为未定义 所以要传递参数 
	int i = 0;
	
	while( str[i] = getchar() )
	{
		if(str[i] == 'q') 
			break;
		i++;
	}
	
	printf("%p\\n",str);				//如果是局部变量虽然地址一样 但内容应该已经被覆盖 
}

CH11 Code answer 2:

#include <stdio.h>

#define SIZE 100
void s_gots(char *);

int main(void)		 
{
	char str[SIZE];
	
	printf("Enter your string(enter space or tab or enter or max character num to quit):"); 
	s_gots(str);
	printf("REVIEW:%s",str);
	
	return 0;
} 

void s_gots(char * str)
{
//	char str[SIZE];						这是局部变量的地址 当用这个地址返回 这个函数的栈帧已经被销毁
//										虽然数据可能还在 但行为未定义 所以要传递参数 
	int i = 0;
	
	while( str[i] = getchar() )
	{
		if(str[i] == '\\n' || str[i] == '\\t' || str[i] == ' ' || i == SIZE-2) 	//在98的时候退出 
		{
//			str[i] = '\\0';					//当字符到str[99]这个字符默认为'/0' 不能改变因为是最后一个字符 
			break;
		}
		i++;
	}
	
	printf("%p\\n",str);				//如果是局部变量虽然地址一样 但内容应该已经被覆盖 
}

CH11 Code answer 3:

#include <stdio.h>
#include <ctype.h>

#define SIZE 20
void s_got(char *);

int main(void)
{
	char str[SIZE];
	
	printf("Enter your character(enter other character to quit):");
	s_got(str);
	printf("The character is '%s'",str); 
	
	return 0;
}

void s_got(char * str)
{
	int i = 0;
	int ch;
	
	while( !isalpha(ch = getchar()) )				//去除缓冲区的空格 
		continue;									//当不成立时 说明第一个字符已经从缓冲区传送到ch中 
	
	str[i++] = ch;
	while( isalpha(ch = getchar()) )				//为什么当结尾不成立时还是会赋值？？ 
		str[i++] = ch; 
	str[i] = '\\0';									//这条设置了最后一个字符是\\0
													//但如果最后不成立一个字符成功 那么这个i应该不成立字符之后？？ 
}

CH11 Code answer 4:

#include <stdio.h>
#include <ctype.h>

#define SIZE 10
void s_got(char *,int);

int main(void)
{
	char str[SIZE];
	
	printf("Enter your character(enter other character or max character num to quit):");
	s_got(str,SIZE);						//要确保数组元素比字符多一 
	printf("The character is '%s'",str); 
	
	return 0;
}

void s_got(char * str,int n)
{
	int i = 0;
	int ch;
	
	while( !isalpha(ch = getchar()) )				//去除缓冲区的空格 
		continue;
	do
	{
		str[i++] = ch; 
	}while( isalpha(ch = getchar()) && i < n-1);	//空出一字节放'\\0'  也就是最多0 ~ 8 
}

CH11 Code answer 5:

#include <stdio.h>
#include <string.h>

#define SIZE 40
char * s_strchr(char *,char);

int main(void)
{
	char str[SIZE];
	char ch;
	char * pt;
	
	while(pt)
	{
		printf("Please enter the string(error to quit):");
		scanf("%s",str);
		while(getchar() != '\\n')
			continue;
		printf("Please enter the search string:");
		scanf("%c",&ch);
		
		pt = s_strchr(str,ch);
		printf("The localtion of first is '%s'\\n\\n",pt); 
	}
	
	return 0;
} 

char * s_strchr(char * str, char ch)
{
	int i = 0;
	
	while(i < strlen(str))
	{
		if( str[i] == ch )
			return &str[i];
		i++;
	}
	return NULL;
}

CH11 Code answer 6:

#include <stdio.h>
#include <string.h>

#define SIZE 40
int s_strchr(char *,char);

int main(void)
{
	char str[SIZE];
	int pt = 1;
	char ch;
	
	while(pt)
	{
		printf("Please enter the string(error to quit):");
		scanf("%s",str);
		while(getchar() != '\\n')
			continue;
		printf("Please enter the search string:");
		scanf("%c",&ch);
		
		pt = s_strchr(str,ch);
		printf("The localtion of first is '%d'\\n\\n",pt); 
	}
	
	return 0;
} 

int s_strchr(char * str, char ch)
{
	int i = 0;
	
	while(i < strlen(str))
	{
		if( str[i] == ch )
			return 1;
		i++;
	}
	return 0;
}

CH11 Code answer 7:

#include <stdio.h>
#include <string.h>

#define SIZE 10
char * MyStrncpy(char *, char *, int);

int main(void)
{
	char str1[SIZE] = "012345678";						//共十个元素最多九个字符 0~8 
	char str2[SIZE+SIZE];
	char ch = '@';
	
	while(strncmp(str1,&ch,1))
	{
		printf("Please enter the copy string(enter @ to quit):");
		scanf("%s",str2);
		while(getchar() != '\\n')
			continue;
		
		printf("The localtion of first is '%s'\\n\\n",MyStrncpy(str1,str2,SIZE)); 
	}
	
	return 0;
}

char * MyStrncpy(char * str1, char * str2, int n)
{
	int i;
	
	for(i = 0; i < n-1; i++)				//0~8 最后9默认填充\\0 
		str1[i] = str2[i];
	
	return str1;
	
//	strncpy(str1, str2, n-1);				//最多九个字符 也就是0~8 
//	str1[n-1] = '\\0';						//最后一个字符也就是str1[9]存储结束符 
	
	
}

CH11 Code answer 8:

#include <stdio.h>
#include <string.h>

#define SIZE 10
char * string_in(char *, char *);

int main(void)
{
	char str1[SIZE];
	char str2[SIZE];
	char * pt;
	
	while(pt)
	{
		printf("Please enter the first string(error to quit):");
		scanf("%s",str1);
		while(getchar() != '\\n')
			continue;
		printf("Please enter the search string:");
		scanf("%s",&str2);
		while(getchar() != '\\n')
			continue;
		
		pt = string_in(str1,str2);
		printf("The localtion of first is '%s'\\n\\n",pt); 
	}
	
	return 0;
}

char * string_in(char * str1, char * str2)
{
	int i = 0;
	int j;
	
	while( i < strlen(str1))
	{
		if( str2[0] == str1[i] )					//查找第一个字符 
		{	
			for(j = 1; j < strlen(str2); j++) 
			{
				if( str2[j] != str1[i+j] )			//遍历接下里的字符是否符合 
					break;
			} 
			if( strlen(str2) == j )					//当所有符合j会运行到最后没有退出 j相等于str2长度 
				return &str1[i];
		}
		i++;
	}
	
	return NULL;
}

CH11 Code answer 9:

#include <stdio.h>
#include <string.h>

#define SIZE 10
void Reverse(char *);

int main(void)
{
	char str1[SIZE];
	char ch = '@';
	
	while( strncmp(str1, &ch, 1) )
	{
		printf("Enter some need to reverse string(enter @ to quit):");
		scanf("%s",str1);
		Reverse(str1);
		printf("The Reverse string is '%s'\\n\\n", str1);
	}
	
	return 0;
} 

void Reverse(char * str)
{
	int i,b;
	char pz;
	//像这个要思考的是什么！？ 两个下标 一个向上行使 一个向下行使  
	//偶数长度 因为从0开始 直接n/2得到向下行使的下标 于是向上行使的下标(n-1)/2 就可以得到的向下行使下标之前的那个数 于是这两个数就是这个序列最中间的两个数 
	//奇数长度 直接/2和-1/2得到的都是中间的数 于是可以遍历对调 
	for(i = strlen(str)/2, b = (strlen(str)-1)/2; i < strlen(str); i++, b--)	//注意是 < 没有 = 因为从strlen不是从0开始 
	{
		pz = str[i];
		str[i] = str[b];
		str[b] = pz;
	}
}

CH11 Code answer 10:

#include <stdio.h>
#include <string.h>
#include <ctype.h>

#define SIZE 100
void G_String(char *);

int main(void)
{
	char str[SIZE];
	char end = '@';
	int i = 0;
	int j;
	
	while( strncmp(str,&end,1)) 
	{													 
		printf("Please enter the string(enter @ to quit):");
		while( str[i] = getchar(), i < SIZE - 1 )
		{
			if( str[i] == '\\n' )
				if( (str[++i] = getchar() ) == '\\n' )
					break;
			i++;
		}
		while( getchar() != '\\n' )									//清空缓冲区 
			continue;
		G_String(str);
		printf("\\nNow give you '%s'\\n\\n",str);
		for( i = SIZE - 2; i > 0 ; --i)							//清空字符串 i下标也重置为0 
			str[i] = 0;
	}

	return 0;	
} 

void G_String(char * str)
{
	int i,b;
	
	for( i = 0, b = 0; b < strlen(str); b++)
		if( isalpha(str[b]) )
			str[i++] = str[b];
	str[i] = '\\0';
}

CH11 Code answer 11:

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>

#define ROWS 10
#define COLS 100

char * s_gets(char * st, int n);
void Print_msg(void);
void G_ar(char (*ar)[COLS],char * ptrstr[]);	//如果*ar[COLS]结合律是[]优先 那么变成指向COLS长度长的指针数组 
void Print(char * ptrstr[]);
void Asc(char * ptrstr[]);						//这个函数比较的是字符串首字母 而直接传入用strcmp会有const char问题
												//于是按书上办法来 传入一个指针数组 那么也就需要新创建一个变量 
void Len(char * ptrstr[]);						//根据字符串长度排序 
void F_ch(char (*ar)[COLS]);
int String_in(char * str1,char * str2);

int main(void) 
{
	int ch;
	char ar[ROWS][COLS];
	char * ptrstr[ROWS];
	
	printf("Please enter ten string:\\n");
	G_ar(ar, ptrstr);
	Print_msg();
	while(1)
	{	
		printf("Your choose is ");
		scanf("%d",&ch);
		while(getchar() != '\\n')				//遇事不决 缓冲区背锅 
			continue;	
		if( ch > 0 && ch < 5)
		{		
			switch (ch)
			{
				case 1:
					Print(ptrstr);
					break;
				case 2:
					Asc(ptrstr);
					Print(ptrstr);
					break;
				case 3:
					Len(ptrstr);
					Print(ptrstr);
					break;
				case 4:
					F_ch(ar);
					break;
			}
			Print_msg();
		}
		else if( ch == 5 )
		{
			printf("bye!");
			break;
		}	
		else
		{
			printf("Please enter 1~5\\n"); 
			Print_msg();
		}
	}
	
	
	return 0;
}

void Print_msg(void)
{
	printf("\\n");
	printf("***********************************************\\n");
	printf("1.Print          2.Print(Ascil)\\n");
	printf("3.Print(len)     4.Print(First character len)\\n");
	printf("5.Quit\\n");
	printf("***********************************************\\n");	
} 

void G_ar(char (*ar)[COLS], char *ptrstr[ROWS])
{
	int ct = 0;
	
	while(ct < ROWS && s_gets(ar[ct], COLS) != NULL && ar[ct][0] != '\\0')
	{
		ptrstr[ct] = ar[ct];
		ct++;
	}
}

void Print(char * ptrstr[])
{
	int i;
	
	for(i = 0; i < ROWS; i++)
			printf("The %-3d string is %s\\n",i + 1, ptrstr[i]);
}

void Asc(char * ptrstr[])
{
	int i, j;
	char * tmp;
	
	for( i = 0; i < ROWS - 1; i++)
		for( j = i + 1; j < ROWS; j++)
			if( strcmp(ptrstr[i],ptrstr[j]) > 0 )
			{
				tmp = ptrstr[i];
				ptrstr[i] = ptrstr[j];
				ptrstr[j] = tmp;
			}
}

char * s_gets(char * st, int n)
{
	char * ret_val;
	
	ret_val = fgets(st, n, stdin);
	if(ret_val)
	{
		while(*st != '\\n' && *st != '\\0')
			st++;
		if(*st == '\\n')
			*st = '\\0';
		else
			while( getchar() != '\\0')
				continue;	
	}	
	
	return ret_val;
}

void Len(char * ptrstr[])
{
	int i, j;
	char * tmp;
	
	for(i = 0; i < ROWS - 1; i++)
		for(j = i + 1; j < ROWS; j++)
			if( strlen(ptrstr[i]) > strlen(ptrstr[j]) )
			{
				tmp = ptrstr[i];
				ptrstr[i] = ptrstr[j];
				ptrstr[j] = tmp;	
			} 
}

void F_ch(char (*ar)[COLS])
{
	int i,j,a,b;
	char ch[ROWS][COLS] = {0};								//要记得初始化单词数组 要不然会有奇怪字符		
	char c;
	char * tmp;
	char * ptr[ROWS];
	
	for(i = 0, a = 0, j = 0, b = 0; i < ROWS; i++, a++)		//将第一个单词放入数组 
	{
		while( !isalpha(c = ar[i][j]))//去掉空格 
			j++;
		ch[a][b++] = ar[i][j++];	//获取已经是字母是单词首尾 然后j加到下个字符 
		while( isalpha( c = ar[i][j++] ) )	//存入所有单词 直到遇到第一个空格 
			ch[a][b++] = c;
		b = 0;
		j = 0;
		ptr[i] = ch[i];										//思路从下面到这 从这里直接赋值到指针数组 
	}
	
/*	
	for( i = 0; i < ROWS - 1; i++)							//排序单词数组 
		for( j = i + 1; j < ROWS; j++)
			 if( strlen(ch[i]) > strlen(ch[j]))				//直接写这样的替换不行 因为这是指针数组操作 
			 {
			 	tmp = ch[i];
			 	ch[i] = ch[j];
			 	ch[j] = tmp;
			 }
*/	
	Len(ptr); 												//调用这个函数成功排序第一个字符 
	for( i = 0; i < ROWS; i++)
		for( j = 0; j < ROWS; j++)
			if(String_in(ar[j], ptr[i]))
			{
				puts(ar[j]);
				break;
			}
}

//这个和strstr应该是相同功能 但不能正常返回？？看麻了下次找 		找到咯 
int String_in(char * str1, char * str2)
{
	int i = 0;
	int j;

	while( i < strlen(str1))					//之前把i++放在这 
	{
		if(str2[0] == str1[i])					//当在这的时候str1[i]就成1了于是不能从第0位开始 
		{
			for( j = 1; j < strlen(str2); j++)
			{
				if(str2[j] != str1[i+j])
					break;
			}
			if( strlen(str2) == j )
			{
				return 1;
			}		
		}
		i++;									//应该是第一个字符判断之后再加 
	}
	
	return 0;
}

CH11 Code answer 12:

#include <stdio.h>
#include <ctype.h>
#include <string.h>

#define SIZE 100 
int Word_num(char *);

int main(void)
{
	int num = 0, low = 0, up = 0, bd = 0, wdnum = 0;
	int i = 0;
	char str[SIZE] = {0};
	
	printf("Please enter a string:"); 
	while( (str[i] = getchar()) != EOF) 
	{
		if(isdigit(str[i]))
			num++;
		if(islower(str[i]))
			low++;
		if(ispunct(str[i]))
			bd++;
		if(isupper(str[i]))
			up++;
		i++;
	}
	wdnum = Word_num(str);
	printf("The word num hava %d\\nThe num have %d\\nThe lower character have %d\\nThe punction have %d\\nThe The upper character have %d"
			,wdnum,num,low,bd,up);
	
	return 0; 
} 

int Word_num(char * str)
{
	int i, num, flag;
	
	for(i = 0, num = 0, flag = 0; i < strlen(str); i++)
	{
		if(flag == 0 && isalpha(str[i]))					//单词开头是字符 flag为0(单词还没开始) 
			flag = 1;					//flag设为1单词开始 
		if(flag == 1 && isspace(str[i]))					//状态为是单词状态 而且到了有 空 说明单词结束
		{													
			num++;
			flag = 0;					//flag设为0单词结束 
		} 
	} 
	
	return num;
}

CH11 Code answer 13:

#include <stdio.h>
#include <ctype.h> 
#include <string.h>

#define SIZE 100
#define CHNUM 10 
int Re_String(char *, char (*ch)[SIZE]);

int main(void)
{
	char str[SIZE];
	char  ch[CHNUM][SIZE] = {0};
	int count;
	
	printf("Please enter a string:");
	fgets(str,SIZE,stdin);
	count = Re_String(str, ch);	 
	while(count--)
		printf("%s ",ch[count]);
		
	return 0;
}

int Re_String(char * str, char (*ch)[SIZE])
{
	int flag, i, a, b;
	
	for(i = 0, flag = 0, a = -1, b = 0; i < strlen(str); i++, b++)
	{
		if(flag == 0 && isalpha(str[i]))
		{
			flag = 1;
			a++;				//新的一个单词 
			b = 0;				//二维下标重新重置为0 
		}
		if(flag == 1 && isspace(str[i]))
			flag = 0;
		if(flag)
			ch[a][b] = str[i]; 		//存储每个单词 
	}
	
	return a + 1;		//返回个数 因为主函数中用while判断0 所以+1个数 
}

CH11 Code answer 14:

#include <stdio.h>

double Pow(double, int);

int main(void)
{
	double kk = 1;
	int n;
	
	while(kk)
	{
		printf("Please enter your num(enter 0 to quit):");
		scanf("%lf",&kk);
		printf("Please enter the n:");
		scanf("%d",&n);
		printf("The answer is %lf\\n",Pow(kk,n)); 	
	}
	
	
	return 0;
} 

double Pow(double kk, int n)
{
	int i;
	double pz = 1;
	
	for(i = 1; i <= n; i++)
	{
		pz = pz *kk;
	}
	
	return pz;
}

CH11 Code answer 15:

#include <stdio.h>
#include <string.h>
#include <ctype.h>

#define SIZE 10
int s_atoi(char *);
int Pow(int, int);

int main(void)
{
	char str[SIZE];
	int num = 1;
	
	while(num)
	{
		printf("Please enter the num(enter !num to quit):");
		scanf("%s",str);
		num = s_atoi(str);
		printf("%d\\n", num);
	}
	
	return 0;
}

int s_atoi(char * str)
{
	int num, i;
	char ch;
	
	for(i = 0, num = 0; i < strlen(str); i++)
	{
		if(!isdigit(str[i]))
			return 0;
		ch = str[i];
		num += ((int)ch - 48) * Pow(10, (strlen(str) - i - 1));	
	}
	
	return num; 
}

int Pow(int kk,int n)
{
	int i, pz;
	
	for(i = 0, pz = 1; i < n; i++)
	{
		pz *= kk;
	}
	
	return pz;
}

CH11 Code answer 16:

#include <stdio.h>
#include <string.h> 
#include <ctype.h>

int main(int argc, char * argv[])		//猜想是如果不打参数 会把 '<' 当成参数 然后文件也导入不进不去 
{
	char ch;
	
	if(*argv[1])
	{
		switch (*argv[1])
		{
			case 'p':
				while((ch = getchar()) != '@')
					putchar(ch);
				return 0;
		
			case 'u':
				while((ch = getchar()) != '@')
					putchar(toupper(ch));
				return 0;
		
			case 'l':
				while((ch = getchar()) != '@')
					putchar(tolower(ch));
				return 0;
		} 
	}
	
	while((ch = getchar()) != '@')
		putchar(ch);
		
	return 0;
}