The C programming language (second edition,K&R) exercise（CHAPTER 2）

qqssss121dfd2024-04-15 11:18

E x c e r c i s e 2 − 1 Excercise\quad 2-1 Excercise2−1：输出结果如图1和图2所示，这道练习题需要文章1和文章2的知识。

c 复制代码 
#include <stdio.h>
#include <limits.h>


float getFloat(char sign, unsigned char exp, unsigned mantissa);
double getDouble(char sign, unsigned short exp, unsigned long long mantissa);

int main(void)
{
	printf("sizeof(char)=%d\n",sizeof(char));
    printf("Signed char[%d to %d]\n", (~(((unsigned char)~0) >> 1)), (unsigned char)(((unsigned char)~0 >> 1)));
    printf("Unsigned char[0 to %u]\n", ((unsigned char)~0));		
	printf("sizeof(short)=%d\n",sizeof(short));
    printf("Signed short[%d to %d]\n", (~(((unsigned short)~0) >> 1)), (unsigned short)(((unsigned short)~0 >> 1)));
    printf("Unsigned short[0 to %u]\n", (unsigned short)((unsigned short)~0));
	printf("sizeof(int)=%d\n",sizeof(int));
    printf("Signed int[%d to %d]\n", (unsigned int)(~(((unsigned int)~0) >> 1)), (unsigned int)(((unsigned int)~0 >> 1)));
    printf("Unsigned int[0 to %u]\n", (unsigned int)((unsigned int)~0));
	printf("sizeof(long)=%d\n",sizeof(long));
    printf("Signed long[%ld to %ld]\n",(unsigned long)(~(((unsigned long)~0) >> 1)), (unsigned long)(((unsigned long)~0 >> 1)));
    printf("Unsigned long[0 to %lu]\n",(unsigned long)((unsigned long)~0));
	printf("sizeof(long long)=%d\n",sizeof(long long));
    printf("Signed long long[%lld to %lld]\n", (unsigned long long)(~(((unsigned long long)~0) >> 1)), (unsigned long long)(((unsigned long long)~0 >> 1)));
    printf("Unsigned long long[0 to %llu]\n", (unsigned long long)((unsigned long long)~0));

	printf("---------------------------------------------------------------\n");
    printf("Signed char[%d to %d]\n", SCHAR_MIN, SCHAR_MAX);
    printf("Unsigned char[0 to %u]\n", UCHAR_MAX);		
	printf("---------------------------------------------------------------\n");
    printf("Signed short[%d to %d]\n", SHRT_MIN, SHRT_MAX);
    printf("Unsigned short[0 to %u]\n", USHRT_MAX);
	printf("---------------------------------------------------------------\n");
    printf("Signed int[%d to %d]\n", INT_MIN, INT_MAX);
    printf("Unsigned int[0 to %u]\n", UINT_MAX);
	printf("---------------------------------------------------------------\n");
    printf("Signed long[%ld to %ld]\n",LONG_MIN, LONG_MAX);
    printf("Unsigned long[0 to %lu]\n",ULONG_MAX);
	printf("---------------------------------------------------------------\n");
    printf("Signed long long[%lld to %lld]\n", LLONG_MIN, LLONG_MAX);
    printf("Unsigned long long[0 to %llu]\n", ULLONG_MAX);

	printf("---------------------------------------------------------------\n");

    printf("Positive Normalized Float[%g to %g]\n", getFloat(0, 0x01, 0x00000000), getFloat(0, 0xFE, 0x007FFFFF));
    printf("Negative Normalized Float[%g to %g]\n", getFloat(1, 0xFE, 0x007FFFFF), getFloat(1, 0x01, 0x00000000));

    printf("Positive De-Normalized Float[%g to %g]\n", getFloat(0, 0x00, 0x00000001), getFloat(0, 0x00, 0x007FFFFF));
    printf("Negative De-Normalized Float[%g to %g]\n", getFloat(1, 0x00, 0x007FFFFF), getFloat(1, 0x00, 0x00000001));

    printf("Positive De-Normalized Zero Float[%g]\n", getFloat(0, 0x00, 0x00000000));
    printf("Negative De-Normalized Zero Float[%g]\n", getFloat(1, 0x00, 0x00000000));
	
    printf("Positive Infinity Float[%g]\n", getFloat(0, 0xFF, 0x00000000));
    printf("Negative Infinity Float[%g]\n", getFloat(1, 0xFF, 0x00000000));	
	
    printf("Not A Number Float[%g]\n", getFloat(0, 0xFF, 0x00000010));		
    printf("Not A Number Float[%g]\n", getFloat(1, 0xFF, 0x00000001));		

    printf("Positive Normalized Double[%g to %g]\n", getDouble(0, 0x0001, 0x0000000000000000), getDouble(0, 0x07FE, 0x000FFFFFFFFFFFFF));
    printf("Negative Normalized Double[%g to %g]\n", getDouble(1, 0x07FE, 0x000FFFFFFFFFFFFF), getDouble(1, 0x0001, 0x0000000000000000));

    printf("Positive De-Normalized Double[%g to %g]\n", getDouble(0, 0x0000, 0x0000000000000001), getDouble(0, 0x0000, 0x000FFFFFFFFFFFFF));
    printf("Negative De-Normalized Double[%g to %g]\n", getDouble(1, 0x0000, 0x000FFFFFFFFFFFFF), getDouble(1, 0x0000, 0x0000000000000001));

    printf("Positive De-Normalized Zero Double[%g]\n", getDouble(0, 0x0000, 0x0000000000000000));
    printf("Negative De-Normalized Zero Double[%g]\n", getDouble(1, 0x0000, 0x0000000000000000));
	
    printf("Positive Infinity Double[%g]\n", getDouble(0, 0x07FF, 0x0000000000000000));
    printf("Negative Infinity Double[%g]\n", getDouble(1, 0x07FF, 0x0000000000000000));	
	
    printf("Not A Number Double[%g]\n", getDouble(0, 0x07FF, 0x0000000000000010));		
    printf("Not A Number Double[%g]\n", getDouble(1, 0x07FF, 0x0000000000000001));		
    return 0;
}

float getFloat(char sign, unsigned char exp, unsigned mantissa)
{
    unsigned f = ((unsigned)(((unsigned)(sign != 0))) << 31) | ((unsigned)(((unsigned)exp) << 23)) | ((unsigned)(mantissa & 0x007FFFFF));
    return *((float *)&f);
}

double getDouble(char sign, unsigned short exp, unsigned long long mantissa)
{
    unsigned long long d = ((unsigned long long)(((unsigned long long)(sign != 0)) << 63)) | ((unsigned long long)((unsigned long long)(exp & 0x07FF) << 52)) | ((unsigned long long)(mantissa & 0x000FFFFFFFFFFFFF));
    return *((double *)&d);
}


图1.
　
图2.

E x c e r c i s e 2 − 2 Excercise\quad 2-2 Excercise2−2：

c 复制代码 
#include <stdio.h>

#define MAXLINE  (1000)

int getline(char s[], int lim);

int main()
{
    int len;    /* current line length */
    char line[MAXLINE];     /* current input line */

    while ((len = getline(line, MAXLINE)) > 0) 
	{
        printf("%s",line);
    }

    return 0;
}

/* getline: read a line s, return length */
int getline(char s[], int lim)
{
    int c, i;

    for (i = 0; i < lim-1; ++i)
	{
	    c = getchar();	
		if((c == '\n'))
		{
			break;
		}
		else if((c== EOF))
		{
			break;
		}		
		else
		{
            s[i] = c;			
		}
	}
    if (c == '\n') {
        s[i] = c;
        ++i;
    }
    s[i] = '\0';

    return i;
}

E x c e r c i s e 2 − 3 Excercise\quad 2-3 Excercise2−3：

c 复制代码 
#include <stdio.h>

#define MAXLINE  (1000)

int getline(char s[], int lim);
int htoi(char s[]);

int main()
{
	int result=0;
    int len;    /* current line length */
    char line[MAXLINE];     /* current input line */

    while ((len = getline(line, MAXLINE)) > 0) 
	{
        printf("%s\n",line);
		result=htoi(line);
        printf("result=%d\n",result);		
    }

    return 0;
}

int power(int ex)
{
    int i=0;
    int result=1;	
	while(i<ex)
	{
		result=result*16;	
        i=i+1;		
	}
    return result;
}

int htoi(char s[])
{
    int i=0;	
    int result=0;	
    int prefix=0;	
    int s_index=0;
	int e_index=0;
	
    while(s[i]!='\0')
	{
		if(((s[i]>='0')&&(s[i]<='9'))||((s[i]>='a')&&(s[i]<='f'))||((s[i]>='A')&&(s[i]<='F')))
		{
			
		}
		else
		{
			if(i==1)
			{
				if(s[0]=='0')
				{
				    if((s[1]=='x')||(s[1]=='X'))
				    {
				    	prefix=1;
				    	
				    }
					else
					{
					    printf("Hexadecimal string error\n");
                        return -1;						
					}
					
				}
				else
				{
					printf("Hexadecimal string error\n");
                    return -1;						
				}
			}
			else
			{
		        printf("Hexadecimal string error\n");
                return -1;
			}			
		}
	    i=i+1;			
	}	
    s_index=i;	
	if(s_index==0)
	{
		printf("Hexadecimal string error\n");
		return -1;
	}
	if(s_index==1)
	{
		if((s[i]>='0')&&(s[i]<='9'))
		{
		    return  ((int)(s[i]-'0'));	
		}		
		if((s[i]>='a')&&(s[i]<='f'))
		{
		    return  ((int)((s[i]-'a')+10));				
		}
		if((s[i]>='A')&&(s[i]<='F'))
		{
		    return  ((int)((s[i]-'A')+10));				
		}				
	}	
	if(s_index==2)
	{		
		if(prefix==1)
		{
		    printf("Hexadecimal string error\n");
		    return -1;	
		}
        else
		{
		    for(i=0;i<s_index;i++)
			{
		        if((s[s_index-1-i]>='0')&&(s[s_index-1-i]<='9'))
		        {
		            result=result +  ((int)(s[s_index-1-i]-'0')) *power(i);	
		        }		
		        if((s[s_index-1-i]>='a')&&(s[s_index-1-i]<='f'))
		        {
		            result=result +  ((int)((s[s_index-1-i]-'a')+10)) *power(i);										
		        }
		        if((s[s_index-1-i]>='A')&&(s[s_index-1-i]<='F'))
		        {
		            result=result +  ((int)((s[s_index-1-i]-'A')+10)) *power(i);									
		        }					
			}					
		}					
	}
	if(s_index>2)
	{		
		if(prefix==1)
		{
		    for(i=0;i<(s_index-2);i++)
			{
		        if((s[s_index-1-i]>='0')&&(s[s_index-1-i]<='9'))
		        {
		            result=result +  ((int)(s[s_index-1-i]-'0')) *power(i);	
		        }		
		        if((s[s_index-1-i]>='a')&&(s[s_index-1-i]<='f'))
		        {
		            result=result +  ((int)((s[s_index-1-i]-'a')+10)) *power(i);										
		        }
		        if((s[s_index-1-i]>='A')&&(s[s_index-1-i]<='F'))
		        {
		            result=result +  ((int)((s[s_index-1-i]-'A')+10)) *power(i);									
		        }					
			}					
		}	
        else
		{
		    for(i=0;i<s_index;i++)
			{
		        if((s[s_index-1-i]>='0')&&(s[s_index-1-i]<='9'))
		        {
		            result=result +  ((int)(s[s_index-1-i]-'0')) *power(i);	
		        }		
		        if((s[s_index-1-i]>='a')&&(s[s_index-1-i]<='f'))
		        {
		            result=result +  ((int)((s[s_index-1-i]-'a')+10)) *power(i);										
		        }
		        if((s[s_index-1-i]>='A')&&(s[s_index-1-i]<='F'))
		        {
		            result=result +  ((int)((s[s_index-1-i]-'A')+10)) *power(i);									
		        }					
			}					
		}					
	}

    return result;
}


/* getline: read a line s, return length */
int getline(char s[], int lim)
{
    int c, i;

    for (i = 0; i < lim-1; ++i)
	{
	    c = getchar();	
		if((c == '\n'))
		{
			break;
		}
		else if((c== EOF))
		{
			break;
		}		
		else
		{
            s[i] = c;			
		}
	}
    if (c == '\n') {
        s[i] = c;
        ++i;
    }
    s[i] = '\0';

    return i;
}

E x c e r c i s e 2 − 4 Excercise\quad 2-4 Excercise2−4：

c 复制代码 
#include <stdio.h>

#define MAXLINE  (1000)

int getline(char s[], int lim);
void squeeze(char s1[],char s2[]);

int main()
{
	int result=0;
    int len;    /* current line length */
    char line[MAXLINE];     /* current input line */

    while ((len = getline(line, MAXLINE)) > 0) 
	{
        printf("before:%s\n",line);
		squeeze(line,"aFEb");
        printf("after:%s\n",line);		
    }

    return 0;
}

int is_str_ch(char s[],char c)
{
    int i=0;
    char temp_c=0;	
    int result=0;	
	while((temp_c=s[i++])!='\0')
	{   
        if(temp_c==c)
		{
		    result=1;
            break;			
		}	
	}
    return result;
}


void squeeze(char s1[],char s2[])
{
    int i,j;
	for(i=j=0;s1[i]!='\0';i++)
	{			
	    if(!is_str_ch(s2,s1[i]))
        {
			s1[j++]=s1[i];		
		}				
	}
	s1[j]='\0';		
}


/* getline: read a line s, return length */
int getline(char s[], int lim)
{
    int c, i;

    for (i = 0; i < lim-1; ++i)
	{
	    c = getchar();	
		if((c == '\n'))
		{
			break;
		}
		else if((c== EOF))
		{
			break;
		}		
		else
		{
            s[i] = c;			
		}
	}
    if (c == '\n') {
        s[i] = c;
        ++i;
    }
    s[i] = '\0';

    return i;
}

E x c e r c i s e 2 − 5 Excercise\quad 2-5 Excercise2−5：

c 复制代码 
#include <stdio.h>

#define MAXLINE  (1000)

int getline(char s[], int lim);
int any(char s1[],char s2[]);

int main()
{
	int position=0;
    int len;    /* current line length */
    char line[MAXLINE];     /* current input line */

    while ((len = getline(line, MAXLINE)) > 0) 
	{
		position=any(line,"aFEb");
        printf("position=%d\n",position);		
    }

    return 0;
}


int any(char s1[],char s2[])
{
    int i,j;
	for(i=0;s1[i]!='\0';i++)
	{			
	    for(j=0;s2[j]!='\0';j++)
        {
			if(s1[i]==s2[j])
			{
				return i;				
			}				
		}				
	}
	return -1;		
}


/* getline: read a line s, return length */
int getline(char s[], int lim)
{
    int c, i;

    for (i = 0; i < lim-1; ++i)
	{
	    c = getchar();	
		if((c == '\n'))
		{
			break;
		}
		else if((c== EOF))
		{
			break;
		}		
		else
		{
            s[i] = c;			
		}
	}
    if (c == '\n') {
        s[i] = c;
        ++i;
    }
    s[i] = '\0';

    return i;
}

E x c e r c i s e 2 − 6 Excercise\quad 2-6 Excercise2−6：

c 复制代码 
#include <stdio.h>

unsigned setbits(unsigned x,int p,int n,unsigned y);

int main()
{
	unsigned x=0xFFFFFFDF;
	unsigned y=0xFFFFFFF2;
	unsigned p=0;
    p=setbits(x,5,2,y);
    printf("p=%08x\n",p);		

    return 0;
}


unsigned setbits(unsigned x,int p,int n,unsigned y)
{
    unsigned front=((~((unsigned)0))<<(p+1));
    unsigned back=~((~((unsigned)0))<<(p-n+1));
    unsigned all=front | back;	
	x=x & all;	
	y=(~((~0)<<n)) & y;
    y=y<<(p-n+1);
	x=x | y;
	return x;		
}

E x c e r c i s e 2 − 7 Excercise\quad 2-7 Excercise2−7:

c 复制代码 
#include <stdio.h>

unsigned invert(unsigned x,int p,int n);

int main()
{
	unsigned x=0xFFFF55FF;
	unsigned inverted=0;
    inverted=invert(x,15,8);
    printf("inverted=%08x\n",inverted);		

    return 0;
}


unsigned invert(unsigned x,int p,int n)
{
	int i;
    unsigned temp1_x=x & (~((~((~((unsigned)0))<<n))<<(p-n+1)));
    unsigned temp2_x=0;	
    unsigned index=1<<p;
	for(i=0;i<n;i++)
	{
	    if(!(index & x))
		{
			temp2_x|=index;			
		}			
		index=index>>1;		
	}

	return (temp1_x) | (temp2_x);		
}

E x c e r c i s e 2 − 8 Excercise\quad 2-8 Excercise2−8:

c 复制代码 
#include <stdio.h>

unsigned rightrot(unsigned x,int n);

int main()
{
	unsigned x=0xFFFFFF5A;
	unsigned rotated=0;
    rotated=rightrot(x,8);
    printf("rotated=%08x\n",rotated);		

    return 0;
}


unsigned rightrot(unsigned x,int n)
{
    unsigned temp1_x=x & (~((~((unsigned)0))<<n));
	temp1_x=temp1_x<<((sizeof(unsigned) * 8)-n);
    unsigned temp2_x=(x>>n) & ((~((unsigned)0)>>n));	

	return (temp1_x) | (temp2_x);		
}

E x c e r c i s e 2 − 9 Excercise\quad 2-9 Excercise2−9:当 x x x为奇数的时候， x x x的二进制表示的最低位肯定为1，那么此时 x − 1 x-1 x−1的值二进制表示和 x x x的二进制表示基本一样，除了二进制表示的最低位为0，那么此时操作 x & = ( x − 1 ) x\&=(x-1) x&=(x−1)就会将 x x x的二进制表示的最低位清零，其它位保持不变。假设此时 x = 213 x=213 x=213，那么它的二进制表示为 11010101 11010101 11010101，此时 x − 1 x-1 x−1的值二进制表示为 11010100 11010100 11010100，那么此时操作 x & = ( x − 1 ) x\&=(x-1) x&=(x−1)之后 x x x的值为 11010100 11010100 11010100= x − 1 x-1 x−1。当 x x x为偶数的时候， x − 1 x-1 x−1会将 x x x的二进制表示的最右的比特值为1的比特位的值变成0，同时将 x x x的二进制表示的最右的比特值为1的比特位后面所有为0的比特位的值都变成1，因此总的来说操作 x & = ( x − 1 ) x\&=(x-1) x&=(x−1)会将 x x x的二进制表示的最右的比特值为1的比特位清零，其它位保持不变。假设此时 x = 208 x=208 x=208，那么它的二进制表示为 11010000 11010000 11010000，此时 x − 1 x-1 x−1的值二进制表示为 11001111 11001111 11001111，那么此时操作 x & = ( x − 1 ) x\&=(x-1) x&=(x−1)之后 x x x的值为 11000000 11000000 11000000。因此总结来说不论 x x x为奇数还是偶数，操作 x & = ( x − 1 ) x\&=(x-1) x&=(x−1)都会将 x x x的二进制表示的最右的比特值为1的比特位清零，因此可以利用这个现象来统计 x x x中比特位的值为1的比特位的个数。

c 复制代码 
#include <stdio.h>

int bitcount(unsigned x);

int main()
{
	unsigned x=0x84211234;
	unsigned num_of_1_bits=0;
    num_of_1_bits=bitcount(x);
    printf("num_of_1_bits=%d\n",num_of_1_bits);		

    return 0;
}


/* bitcount:  count 1 bits in x */
int bitcount(unsigned x)
{
    int b;

    for (b = 0; x != 0; x &= (x-1))
        b++;
    return b;
}

E x c e r c i s e 2 − 10 Excercise\quad 2-10 Excercise2−10:

c 复制代码 
#include <stdio.h>

char lower(char c);

int main()
{
	char c='A';
    printf("lower(c)=%c\n",lower(c));		
    return 0;
}


/* lower:  convert c to lower case: ASCII only */
char lower(char c)
{
    return ((c>='A' && c<='Z') ? (c-'A'+'a'):c);
}
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