本文全部公式采用mathjax渲染，观感极佳

第一章:

problems 1.7:

problems 1.8:

problems 1.9:

problems 1.12:

第二章:

problems 2.3:

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4th 不是 , 以数字开头

sizeof 不是 , 标准C的关键字

x*y 不是，* 非法

temp-2 不是，- 非法

isn't 不是，' 非法

enum 不是, 标准C的关键字

problems 2.4:

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2L 合法，long长整型

''' 不合法，单引号组中的单引号前需要转义字符

.12 合法，double双精度浮点型

0x1ag 不合法，g不是16进制数中的符号，也不表示任何类型

33333 合法，int整形

"a" 合法，字符串常量

"" 合法，字符串常量

0.L 合法，long double长双精度浮点型

E20 不合法，缺少尾数部分

0377UL 合法，unsigned long无符号长整型

'\18' 不合法，存在非8进制位

'\0xa' 不合法，不符合十六进制字符码表示规则

0x9cfU 合法，unsigned int无符号整形

'\45' 合法，char字符型

1.E-5 合法，double双精度浮点型

'\0' 合法，char字符型

3.F 合法，float浮点型

"3'4"" 不合法，缺少转义符

'"' 合法，char字符型

'\a' 合法，char字符型

problems 2.6:

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(1)int a; b = 5; 第一个分号改为逗号int a, b=5;

(2)doubel h; 关键字错误double h;

(3)int x = 2.3; 类型错误float x = 2.3;

(4)const long y; 需要赋初值const long y = 0;

(5)float a = 2.5*g; g未定义变量

(6)int a = b = 2; b未定义变量int a = 2, b = 2;

problems 2.7:

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(1)++a*b-- -> 4

(2)!a+b/c -> 0

(3)a==-b+c -> true(或者1)

(4)d=a++,a*=b+1 -> d = 1 , a = 6

(5)d=y+=1/x y为8.2, d为8

(6)a<b && x == y -> 1 && 0 -> 0

(7)x=(int)y/b++ x = 3.0

(8)a--?++a:++a a = 1

(9)'a'+'\xa'+a -> 97 + 10 + 1 -> 108

(10)a=0,--a,a+=(a++)-a 表达式结果为-1，a的值为0

problems 2.8:

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(1)a==b==c 错误，c未定义且逻辑错误

(5)a*++-b 错误，++需要左值

(6)a||b^i 错误，^号左侧类型为double

(7)i*j%a 错误，%右侧类型为double

problems 2.10:

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(1)~x&x -> 0

(2)v=~x -2

(3)w=~x^x 65535

(4)x|y&x|z 5

(5)w=y|z,(w<<3)+(w<<1) 60

(6)w=x|y&x|z<>x 113

(7)v=-1,v<<=1 -2

(8)v=~x|x -1

(9)w=x^~y 65532

(10)x|y|z>>2 3

problems 2.11:

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( k >> 8 ) | ( p << 8 )

problems 2.16:

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( a > b ) ? ( a > c ? a : c ) : ( c > b ? c : b )

problems 2.18:

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( ( a % 3 == 0 ) && (a % 10 == 5) ) ? 1 : 0

第三章:

problems 3.5:

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#include <stdio.h>

int main()
{
    char c ;
    scanf("%c",&c) ;
    if(c >= 'A' && c <= 'F') 
    {
        int tmp = c-'A'+10 ;
        printf("%d",tmp) ;
    }
    else if( c >= 'a' && c <= 'f' ) printf("%d",c-'a'+10) ;
    else printf("%c",c) ;
    return 0;
}

problems 3.7:

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#include <stdio.h>

int main()
{
    unsigned short int k , ans ;
    scanf("%u",&k) ;
    unsigned short int tmp1 = 0xf000 , tmp2 = 0x000f , tmp3 =0x0ff0 ;
    tmp1 = (tmp1 & k ) >> 12 ;
    tmp2 = (tmp2 & k ) << 12 ;
    tmp3 = (tmp3 & k ) ;
    ans = ( tmp1 | tmp2 ) | tmp3 ;
    printf("%d",ans) ;
    return 0 ;
}

第四章:

problems 4.1:

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#include <stdio.h>

int a , b , c ;

int max ( int x , int y )
{return x > y ? x : y ; }

int min ( int x , int y )
{return x < y ? x : y ; }

int main()
{
    scanf("%d%d%d",&a , &b , &c ) ;
    int maxx = max(max(a,b),c) ;
    int minn = min(min(a,b),c) ;
    if( a == b && a < c )
    {
        printf("A %d",a) ;
        return 0;
    }
    if( a < maxx && a > minn ) printf("A %d",a) ;
    if( b < maxx && b > minn ) printf("B %d",b) ;
    if( c < maxx && c > minn ) printf("C %d",c) ;
    return 0;
}

problems 4.3:

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

#define re register
#define maxn 15

int year , month , date , ans ;
int a[maxn] ;

int judge ( int x ) 
{
	if ( x % 4 != 0 ) return 0 ;
	else 
	{
		if ( x % 100 != 0 ) return 1 ;
		else
		{
			if ( x % 400 == 0 ) return 1 ;
			else return 0 ;
		}
	}
}

int main()
{	
	scanf ("%d%d%d", &year , &month , &date ) ;
	a[1] = a[3] = a[5] = a[7] = a[8] = a[10] = a[12] = 31 ;
	a[4] = a[6] = a[9] = a[11] = 30 ;
	if( judge(year) ) a[2] = 29 ;
	else a[2] = 28 ;
	for (re int i = 1 ; i <= month - 1 ; i ++ ) 
		ans += a[i] ;
	ans += date ;
	printf("%d\n",ans) ;
	return 0 ;
}

problems 4.5:

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#include <stdio.h>

#define re register

double x , y ;
char c ;

int main()
{	
	scanf("%lf%lf %c",&x,&y,&c) ;
	if( c == '+' )
		printf("%.6lf",x+y) ;
	if( c == '-' )
		printf("%.6lf",x-y) ;
	if( c == '*' )
		printf("%.6lf",x*y) ;
	if( c == '/' )
	{
		if ( !y ) printf("Error") ;
		else printf("%.6lf",x/y) ;
	}
    if( c == '&' ) printf("Error") ;
	return 0 ;
}

problems 4.9:

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#include <stdio.h>

#define re register
#define maxn 1005

int n ;
int a[maxn] ;

int main()
{	
	scanf("%d",&n) ;
	a[1] = a[2] = 1 ;
	for( re int i = 3 ; i <= n ; i++ )
		a[i] = a[i-1] + a[i-2] ;
	int cnt = 0 ;
	for( re int i = 1 ; i <= n ; i++ )
	{
		printf("%6d",a[i]) ;
		if( ++ cnt == 8 )
		{
			putchar('\n') ;
			cnt = 0;
		}
	}
	return 0 ;
}

problems 4.10:

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#include <stdio.h>
#include <math.h>

#define re register

double pi = 0 , tmp = 1.0 , sign = -1.0 ; 

int main()
{
    while ( fabs( 1 / tmp ) > 1e-5 )
    {
        sign *= (-1) ;
        pi += sign / tmp  ;
        tmp += 2 ;
    }
    printf("%lf", pi * 4 ) ;
    return 0 ;
}

problems 4.11:

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#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define re register
#define ll long long
#define maxn 1005

int n ;
int a[maxn] ;

int gcd ( int x , int y )
{return y ? gcd (y,x%y) : x ;}

int main()
{	
	int a , b ;
	scanf("%d%d",&a,&b) ;
    int tmp = gcd ( a , b ) ;
	printf("%d %d", tmp , a*b/tmp ) ;
	return 0;
}

problems 4.17:

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#include <stdio.h>

#define re register

int main()
{
    int tmp , sum , cnt ;
    for ( re int i = 1 ; i <= 10 ; i++ )
    {
        scanf("%d", &tmp) ;
        if ( tmp > 0 ) 
        {
            cnt ++ ;
            sum += tmp ;
        }
    }
    if( cnt ) printf("numbers = %d , average = %lf \n", cnt , ( 1.0 * sum ) / cnt ) ;
    return 0 ; 
}

第五章:

problems 5.1:

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#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define re register

int sum , first , second , point ;

void game ( )
{
    first = rand() % 6 ; second = rand() % 6 ; 
    sum = first + second ;
    if ( sum == 7 || sum == 11 )
    {
        printf("WIN!\nGama Over .") ;
        return ;
    }
    if( sum == 2 || sum == 3 || sum == 12 ) 
    {
        printf("Lost!\nGame over .") ;
        return ;
    }
    point += sum ;
    if ( point == 7 ) 
    {
        printf("Lost!\nGame over .") ;
        return ;
    }
    if ( point == sum )
    {
        printf("WIN!\nGame Over .") ;
        return ;
    }
    game() ;
}

int main()
{
    srand( (unsigned)time(NULL) ) ;
    game() ;
    return 0 ; 
}

problems 5.6:

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不能，swap传入的是形参，只能在swap函数中使用，无法传回原函数。

problems 5.7:

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(1) p(6) = 6 ; (2) p(6) = 12 ;

problems 5.8:

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int i ;
void fun( long i )
{
	long l = i ;
	{
		float i ;
		i = 3.4 ;
	}
	l = i + 2 ;
}
int *p = &i ;
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Answer:
int型i存储类型为extern:
	第1行声明（定义)，11行使用;
long、float型i存储类型为auto:
	long型i在第二行声明（定义)，4、9行使用;
	float型i在第六行声明（定义)，7行使用。

problems 5.11:

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#include <stdio.h>

#define re register
#define maxn 1005

int n , cnt , tmp ;
int a[maxn] ;
void hailstone ( int x )
{
	printf("%4d",x) ;
	if( ++tmp == 6 ) putchar('\n') , tmp = 0 ;
	if( x == 1 ) 
    {
        cnt ++ ;
        return ;
    }
	if( x % 2 == 0 )
    {
        hailstone ( x / 2 ) ;
        cnt ++ ;
    }
		
	else 
	{
		hailstone ( 3*x + 1 ) ;
		cnt ++ ;
	}
}


int main()
{	
	scanf("%d",&n) ;
	printf("Hailstone generated by %d:\n",n) ;
	hailstone ( n ) ;
	if( cnt % 6 != 0 ) putchar('\n') ;
	printf("Number of hailstone generated:%d",cnt) ;
	return 0;
}

problems 5.13:

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

#define re register
#define maxn 1005

int k ;
char s[maxn] ;

int digit( char s[] , int k )
{
    int cnt = strlen (s) ;
    if ( k > cnt ) return -1 ;
    else return (s[ cnt - k ] - '0' ) ;
}

int main()
{
		scanf("%s %d",s,&k) ;
		printf("%d\n",digit( s , k ) ) ;
		return 0 ;
}

problems 12.1:

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#include <stdio.h>
#include <time.h>
#include <conio.h>

#define re register
#define ll long long
#define il inline 

int n ;

inline ll fib( int n )
{
    if ( n == 1 || n == 2) return 1 ;
    return fib(n - 1) + fib(n - 2) ;
}

int main()
{
    time_t first , second ;
    first = time(NULL) ;
    printf("%lld\n",fib(40)) ;
    second = time(NULL) ;
    printf("The difference is: %f seconds", difftime(second,first)) ;
    return 0 ;
}
//solution : 使用数组对求出的 fib(n) 进行存储

problems 12.3:

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

#define re register
#define maxn 10005

char s[maxn] ;
int cnt ;

void solve( int pos , char s[] ) 
{
    if ( pos == 0 ) 
    {
        printf("%c", s[pos] ) ;
        return ;
    }
    printf("%c", s[pos] ) ;
    solve( pos - 1 , s ) ;
}

int main()
{
    scanf("%s",s) ;
    solve( strlen(s) - 1 , s ) ;
    return 0 ; 
}

第六章

problems 6.1:

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(2) 编译时将 NUMBER 换成 = 20 ;
(3) 编译时将 ident 换成 (x) x ;
(5) 编译时可能忽略优先级

problems 6.4:

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

#define swap(x,y) t=x,x=y,y=t

int t ;

int main()

{
	int a , b ;
	scanf("%d%d",&a , &b ) ;
	swap(a,b) ;
	printf("%d %d",a,b ) ;
	return 0 ;
}

第七章：

problems 7.7:

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#include <stdio.h>

#define re register
#define maxn 100005

int n ;
int a[maxn] , b[maxn] ; 

int max ( int x , int y ) 
{return x > y ? x : y ;} 

void swap ( int *a , int *b ) 
{
    int tmp = *a ;
    *a = *b ;
    *b = tmp ;
}

int main()
{
    scanf("%d",&n) ;
    for( re int i = 1 ; i <= n ; i++ )
        scanf("%d", a + i ) ;
    for( re int  i = 1 ; i <= n ; i++ )
    {
        int maxx = i ;
        for( re int j = i + 1 ; j <= n ;j ++ ) 
        {
            if( a[j] < a[maxx] ) maxx = j ;
        }
        swap ( &a[i] , &a[maxx] ) ;
    }
    for( re int i = 1 ; i <= n ; i++ )
        printf("%d ",a[i] ) ; 
    return 0 ;
}

problems 7.8:

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#include <stdio.h>

#define re register
#define maxn 10005

int n , k ;
int a[maxn] ;

int main()
{
    scanf("%d%d", &n , &k ) ;
    for( re int i = 0 ; i < n ; i++ ) 
    {
        scanf("%d" , &a[i]) ;
    }
    for( re int i = k ; i < n ; i++ )
        printf("%d " , a[i] ) ;
    for( re int i = 0 ; i < k ; i++ )
        printf("%d " , a[i] ) ;
    return 0 ;
}

problems 7.9:

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

#define re register
#define maxn 10005

int cnt , num , alp , other ;

char s[maxn] ;
int main()
{
    scanf("%s",s) ;
    int cnt = strlen (s) ;
    for( re int i = 0 ; i < cnt ; i++ )
    {
        if( s[i] >= '0' && s[i] <= '9' ) num++ ;
        else if( ( s[i] >= 'a' && s[i] <= 'z' ) || ( s[i] >= 'A' && s[i] <= 'Z') 
            alp ++ ;
        else other++ ;
    }
    printf("%d %d %d", num , alp , other ) ;
    return 0;
}

problems 7.13:

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

#define re register
#define maxn 10005

int n ;
char s[maxn] , t[maxn] ;

int min ( int x , int y ) 
{ return x < y ? x : y ;}

void strncpy( char a[] , char b[] , int x ) 
{
    int len_a = strlen(a) , len_b = strlen(b) ;
    for ( re int i = 0 ; i < min( x , len_b ) ; i++ ) 
    {
        a[i] = b[i] ;
    }
    return ;
}

int main()
{
    scanf("%s%s%d", s , t , &n ) ;
    strncpy(s,t,n) ;
    printf("%s",s) ;
    return 0 ;
}

problems 7.15:

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

#define re register
#define maxn 10005

int n ;
char s[maxn] ;

int change (char c)
{
    if(c >= 'A' && c <= 'F') 
        return c-'A'+10 ;
    else if( c >= 'a' && c <= 'f' ) return c-'a'+10 ;
    else return c-'0' ;
}

int main()
{
    int n ;
    scanf("%d",&n) ;
    while ( n-- )
    {
        scanf("%s",s) ;
        int cnt = strlen (s) , ans = 0 , tmp = 0 ;
        for( re int i = cnt - 1 ; i > 1 ; i-- ) 
            ans += change(s[i]) * pow (16,tmp++) ;
        printf("%d ",ans ) ;
    }
    return 0 ;
}

problems 12.5:

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

#define re register 

char s[10005] ;
int flag = 1 ;
int l = 0 ;

void judge ( char s[] , int l , int r ) // solution 1
{
    if( l + 1 == r)
    {
        if( s[l] != s[r] ) flag = 0 ;
        return ;
    }
    if( l == r ) return ;
    if( s[l] != s[r] ) flag = 0 ;
    judge ( s , l + 1 , r - 1 ) ;
}

int IsPalindrom( char arr[] , int len ) // solution 2
{
    if( l + 1 == len)
    {
        if( s[l] != s[len] ) return 0 ;
        return 1 ; 
    }
    if( l == len ) return 1 ;
    if( s[l] != s[len] ) return 0 ;
    l++ ; IsPalindrom( arr , len - 1 ) ;
}

int main()
{
    scanf("%s",s) ;
    // int cnt = strlen(s) ;
    // judge( s , 0 , cnt - 1 ) ;
    printf("%d\n",IsPalindrom( s , strlen(s) - 1 ) ) ;
    return 0;
}