C典型案例及常见错误分析

1、C+简单程序典型案例【案例2-1】设计一个编写仅包含C+程序基本构成元素的程序/*      /注释行开始This is the first C+ program.       Designed by zrf */     /注释行结束#include <iostream>    /包含头文件using namespace std;    /打开命名空间std/ This is the

2、 main function /单行注释语句int main(void)    /主函数，程序入口    /块作用域开始 int age;     /声明一个变量   age= 20;       /赋值语句   cout<<"The age is:n"   /输出一个字符串   cout<

3、<age<<endl;      /输出变量中的值 return 0;     /主函数返回0    /块作用域结束        【案例2-2】计算圆的周长和面积C+语言中常量、变量#include <iostream>using namespace std;int main() const float PI=3.1415926;  /

4、float 型常量 float r=2.0;    /用float 型常量初始化变量 cout<<"r="<<r<<endl;  /输出圆的半径 float length;    /float型变量声明 length=2*PI*r;    /计算圆的周长 cout<<"Length="<<length<<endl; 

5、/输出圆的周长 float area=PI*r*r;   /计算圆的面积 cout<<"Area="<<area<<endl; /输出圆的面积 return 0; 【案例2-3】整数的简单运算除法、求余运算法和增量减量运算符#include <iostream> using namespace std; int main()  int x, y;  x = 10;  y = 3;  cout << x &l

6、t;< " / " << y << " is " << x / y    /整数的除法操作    <<" with x % y is " << x % y << endl;     /整数的取余操作 x +;   -y ;      /使用增量减量运算符 cou

7、t << x << " / " << y << " is " << x / y << "n"     /整数的除法操作    << x << " % " << y << " is " << x % y<<endl;  /整数的取余操作 return 0;  

8、;【案例2-4】多重计数器前置和后置自增运算符#include<iostream>  using namespace std; int main()    int iCount=1; iCount=(iCount+)+(iCount+)+(iCount+); /后置+ cout<<"The first  iCount="<<iCount<<endl; iCount=1; iCount=(+iCoun

9、t)+(+iCount)+(+iCount); /前置+ cout<<"The second iCount="<<iCount<<endl; iCount=1; iCount=-iCount+;    /后置+ cout<<"The third  iCount="<<iCount<<endl; iCount=1; iCount=-+iCount; 

10、0;  /前置+ cout<<"The fourth  iCount="<<iCount<<endl; return 0;  【案例2-5】对整数“10”和“20”进行位运算位运算的应用#include <iostream>using namespace std;int main()        cout << "20&10=" << (20&a

11、mp;10) << endl;  /按位与运算    cout << "2010=" << (2010) << endl;  /按位异或运算    cout << "20|10=" << (20|10) << endl;  /按位或运算    cout << "20=" <<(20

12、) << endl;          /按位取反运算    cout << "20<<3=" << (20<<3) << endl;  /左移位运算    cout << "-20<<3=" << (-20<<3) << endl;  

13、/左移位运算    cout << "20>>3=" << (20>>3) << endl;  /右移位运算    cout << "-20>>3=" << (-20>>3) << endl;  /右移位运算 return 0; 【案例2-6】实现逻辑“异或”运算逻辑运算应用#include <iostream&

14、gt; using namespace std; int main()  bool p, q;  p = true;   q = true;  cout <<p <<" XOR "<<q<<" is "<<( (p | q) && !(p && q) )<< "n" /输出异或结果 p = false;   q = true;  cout &l

15、t;<p<<" XOR "<<q<< " is "<<( (p | q) && !(p && q) )<< "n" /输出异或结果 p = true;   q = false;  cout <<p<<" XOR "<<q<<" is "<<( (p | q) && !(p &&

16、amp; q) )<< "n" /输出异或结果 p = false;   q = false;  cout <<p<<" XOR "<<q<<" is "<<( (p | q) && !(p && q) )<< "n" /输出异或结果 return 0;  【案例2-7】高效筛选器用条件运算符“?”构建条件表达式#include<ios

17、tream>using namespace std;int main()  int iNum1=1,iNum2,iMax; cout<<"Please input two integers:n"    cin>>iNum1>>iNum2; iMax = iNum1>iNum2 ? iNum1 : iNum2;  /使用条件运算符构建条件表达式 cout<<"The max integer is: "<

18、<iMax<<endl;   return 0; 【案例2-8】“多计算与单提取”功能的实现逗号表达式#include<iostream>using namespace std;int main()    int Val1, Val2, Val3, Left, Midd, Righ; Left = 10; Midd = 20;   Righ = 30;   Val1 = (Left+, -Midd, Righ+);   /使用

19、逗号表达式 Val2 = (Righ+, Left+, -Midd);  /使用逗号表达式 Val3 = ( -Midd, Righ+,Left+);  /使用逗号表达式    cout <<"Val1=t"<<Val1 <<"nVal2=t"<<Val2 <<"nVal3=t"<<Val3<<endl;    return 0; 【案例2-9

20、】高效的算术运算符复合赋值运算符#include <iostream>using namespace std;int main() int n=20;  cout << "n = " << n << endl; n += 8;   cout << "After n += 8, n = " << n << endl;  /使用复合的赋值运算符+= n -= 6;   cout <

21、< "After n -= 6, n = " << n << endl;  /使用复合的赋值运算符-= n *= 1;   cout << "After n *= 1, n = " << n << endl; /使用复合的赋值运算符*= n /= 4;   cout << "After n /= 4, n = " << n << endl;  /

22、使用复合的赋值运算符/= n %= 3;  cout << "After n %= 3, n = " << n << endl;  /使用复合的赋值运算符%= return 0; 【案例2-10】计算不同数据类型的存储容量sizeof运算符#include <iostream>using namespace std ;int main() cout << "The size of an int is:tt" << sizeo

23、f(int) << " bytes.n" cout << "The size of a short int is:t" << sizeof(short) << " bytes.n" cout << "The size of a long int is:t" << sizeof(long) << " bytes.n" cout << "The size of a

24、char is:tt" << sizeof(char) << " bytes.n" cout << "The size of a wchar_t is:t" << sizeof(wchar_t) << " bytes.n" cout << "The size of a float is:tt" << sizeof(float) << " bytes.n" cou

25、t << "The size of a double is:t" << sizeof(double) << " bytes.n" return 0; 【案例2-11】巧妙获取整数部分double和int数据类型的转换#include <iostream>using namespace std;int main()   int nn=10,mm;    double xx=4.741,yy;     cout&

26、lt;<"nn*xx="<<nn*xx<<endl;     /表达式类型转换    mm=xx;    yy=nn;         /赋值类型转换    cout<<"mm="<<mm<<endl <<"yy="<<yy<<

27、endl;    cout<<"int(xx)="<<int(xx)<<endl <<"(int)xx="<<(int)xx<<endl;    /强制类型转换    cout<<"int(1.412+xx)="<<int(1.412+xx)<<endl;      /强制类型转换 

28、0;  cout<<"(int)1.412+xx="<<(int)1.412+xx<<endl;     /强制类型转换 return 0; 【案例2-12】将分数转换为小数强制类型转换#include <iostream> using namespace std; int main() for( int i=1; i <= 5; +i )   cout << i << "/ 3 is:

29、" << (float) i / 3 << endl;     /强制类型转换 return 0;  【案例2-13】安全的除法计算器#include <iostream> using namespace std; int main()  int a, b;  cout << "Enter numerator: "    cin >> a;  cout << "En

30、ter denominator: "    cin >> b;  if(b) cout << "Divide Result is: " << a / b << 'n'  /排除除数为零的情况 else cout << "Divide by zero!n"  return 0;  【案例2-14】猜数游戏嵌套的if条件语句#include <iostream> #include &

31、lt;cstdlib> using namespace std; int main()  int MagNum, GueNum;   MagNum = rand();      /产生随机数 cout << "Enter the Guess number: "   cin >> GueNum;  if (GueNum = MagNum)         &#

32、160;/if语句块起始位置  cout << "* It is Right *n"<< MagNum << " is the Magess number.n"         /if语句块结束位置 else          / else语句块起始位置  cout << "Sorry, y

33、ou're wrong."<<endl;   if(GueNum > MagNum)       cout <<"Guessed number is too high.n"   else      cout << "Guessed number is too low.n"        &

34、#160; /else语句块结束位置 return 0;  【案例2-15】根据输入月份输出从年初到本月底的天数不带break的switch#include <iostream>using namespace std;int main() int year,month,days=0; cout<<"Input year and month:"  cin>>year>>month; switch (month)     

35、  /每个case分支均没有break语句   case 12: days +=31;  case 11: days +=30;   case 10: days +=31;  case  9: days +=30;  case  8: days +=31;  case  7: days +=31;  case  6: days +=30;  case  5: days

36、 +=31;  case  4: days +=30;  case  3: days +=31;   case  2:      /判断是否为闰年   if (year % 4=0 && year % 100!=0 | year %400=0)           days +=29;  &#

37、160;else           days +=28;  case  1: days +=31;  if (days=0)    cout<< "Wrong month"<<endl; else     cout << "Total days is:" <<days<&l

38、t; endl; return 0; 【案例2-16】计算数的阶乘do-while循环语句#include <iostream>using namespace std;int main()  long limits;   cout << "Enter a positive integer: "   cin >> limits;   cout << "Factorial numbers of "<<0<

39、<" is " << 1<<endl;   cout << "Factorial numbers of "<<1<<" is " << 1<<endl;   long fac=1, i=1;   do       /使用do-while循环   fac *= +i;   

40、;    cout << "Factorial numbers of "<<i<<" is " << fac<<endl;  while (fac < limits);   return 0; 【案例2-17】计算数的阶乘for循环#include <iostream>using namespace std;int main()  long limits;   cout <<

41、"Enter a positive integer: "   cin >> limits;   cout << "Factorial numbers of "<<0<<" is " << 1<<endl;   cout << "Factorial numbers of "<<1<<" is " << 1<<

42、endl;   long fac=1; for(int i=2;fac<=limits;i+)    /使用for 循环   fac *= i;    cout << "Factorial numbers of "<<i<<" is " << fac<<endl;  return 0; 【案例2-18】筛选素数步长为2的for循环#inclu

43、de <iostream>#include <cstdlib>using namespace std;int main() long n; cout << "Enter a positive integer: "  cin >> n; if (n < 2)      cout << n << " is not prime." << endl; else if (n &

44、lt; 4)      cout << n << " is prime." << endl; else if (n%2 = 0)      cout << n << " = 2*" << n/2 << endl; else  for (int i=3; i <= n/2; i += 2)  /步长为2

45、0;   if (n%i = 0)          cout << n << " = " << i << "*" << n/i << endl;  exit(0);   cout << n << " is prime." << endl;  return 0; 【案例2

46、-19】输出120之间的偶数continue语句#include <iostream> using namespace std; int main()  cout<<"The even numbers are as follows:"<<endl;  for(int i=0; i<=20; i+)   if(i%2) continue;  /根据条件使用continue结束本次循环  cout << i << ' '

47、60;  return 0;  【案例2-20】统计输入整数的个数并求和exit()函数#include <iostream> #include <cstdlib>using namespace std; int main()  int sum=0,num=0,m;  cout<<"Please input integers (0:end):"<<endl;  do cin>>m;   num+;   sum+=m; 

48、;    if(m=0)     cout<<"Entered numbers:"<<num<<" integers.n"   cout<<"The sum is:"<<sum<<endl;   exit(0); / 使用exit()函数终止程序      while(1);&

49、#160;return 0;  【案例2-21】“剪刀、石头、布”游戏枚举类型#include <iostream>using namespace std;enum Choice ROCK, CLOTH, SCISS; /声明枚举类型Choiceenum Winner Play1, Play2, Tie;   /声明枚举类型Winnerint main() int n;    Choice cho1, cho2;     Winner winner; c

50、out << "Choose rock (0), cloth (1), or Sciss (2):" << endl; cout << "Player No. 1: " cin >> n; cho1 = Choice(n); cout << "Player No. 2: " cin >> n; cho2 = Choice(n); if (cho1 = cho2) winner = Tie;

51、60;else if (cho1 = ROCK)  if (cho2 = CLOTH)  winner = Play2;  else  winner = Play1; else if (cho1 = CLOTH)  if (cho2 = SCISS)  winner = Play2;  else  winner = Play1; else   if (cho2 = ROCK)  winner = Play2; 

52、60;else  winner = Play1; if (winner = Tie)   cout << "tTied!n" else if (winner = Play1)  cout << "tPlayer No. 1 wins." <<endl; else  cout << "tPlayer No. 2 wins." << endl; return 0; 【案例2-22】

53、简单的学生信息类型结构体#include <iostream>#include <iomanip>using namespace std;struct student             /学生信息结构体   int num;    char name20;    char gender;    int age; stu1=1001,"Zh

54、ang San",'M',19;int main() student stu2=1002,"Li Si",'M',20;  /声明结构体变量并初始化 student stu3=1003,"Wang Hong",'F',22;         /声明结构体变量并初始化    cout<<setw(7)<<stu1.num<

55、<setw(20)<<<<setw(3)<<stu1.gender<<setw(3)<<stu1.age<<endl; cout<<setw(7)<<stu2.num<<setw(20)<<<<setw(3)<<stu2.gender<<setw(3)<<stu2.age<<endl; cout<<setw(7)<<stu3.num

56、<<setw(20)<<<<setw(3)<<stu3.gender<<setw(3)<<stu3.age<<endl; return 0; 【案例2-23】综合案例百钱买百鸡问题#include<iostream>using namespace std;int main()       int n=100;   cout<<"鸡公  鸡母  鸡雏"&

57、lt;<endl;      /i表示鸡公，j表示鸡母，k表示鸡雏   for ( int i = 1; i <= n; i+ )   for ( int j = 1; j <= n; j+ )    for( int k = 1; k <= n; k+ )     if( n = 5 * i + 3 * j + k / 3 ) && ( k % 3 = 0 ) && ( n =

58、i + j + k )       cout << i << "  " << j << "  " << k << endl;   return 0;#include<stdio.h>int main()   int x,y,z,j=0;   printf("Folleing are possible plans to buy

59、 100 fowls with 100 Yuan.n");   for(x=0;x<=20;x+)         /外层循环控制鸡翁数      for(y=0;y<=33;y+)      /内层循环控制鸡母数y在033变化             &#

60、160; z=100-x-y;           /内外层循环控制下，鸡雏数z的值受x,y的值的制约         if(z%3=0&&5*x+3*y+z/3=100)        /验证取z值的合理性及得到一组解的合理性         

61、;      printf("%2d:cock=%2d hen=%2d chicken=%2dn",+j,x,y,z);      【案例3-1】编写输出专用函数无参函数#include<iostream>using namespace std;void DispMessage(void)               

62、;     /定义无参函数    cout<<"This is a Message!"<<endl;       int main()     DispMessage();                  

63、0;         /调用无参函数DispMessage    return 0; 【案例3-2】编写求和函数有参函数#include<iostream>using namespace std;double add(double x,double y)                    /定义有参函数

64、    double z;    z=x+y;    return(z); int main()       double a=0.5, b=1.0;    cout<<"add(a,b)="<<add(a,b)<<endl;   /调用有参函数add()    return 0; 【案例3-3】编写求和函数函数的不同调用

65、形式#include<iostream>using namespace std;double add(double x,double y)                    /函数的定义，其有返回值       double z;    z=x+y;    cout<<x<&

66、lt;"+"<<y<<"="<<z<<endl;    return(z);int main()    double a=0.5,b=1.0;/以不同参数形式调用函数add()    cout<<"add(1.5,2.5)="<<add(1.5,2.5)<<endl;    cout<<"add(a,b)=&qu

67、ot;<<add(a,b)<<endl;    cout<<"add(2*a,a+b)="<<add(2*a,a+b)<<endl;    double c=2*add(a,b);                       &#

68、160;             /以表达式方式调用函数add()    cout<<"c="<<c<<endl;    add(2*a,b);                   &

69、#160;                                 /以语句方式调用函数add()    cout<<" add(a, add(a,b)="<<add(a, add(a,b)<<e

70、ndl;       /以函数参数形式调用函数add()    return 0; 【案例3-4】编写符号函数函数的返回值#include<iostream>using namespace std;int sgn(double x)                      &

71、#160;/定义符号函数sgn()，其返回值为int类型       if (x>0) return(1);                  /返回出口1    if (x<0) return(-1);            

72、    /返回出口2    return(0);                             /返回出口3int main()       double x;    &

73、#160; for (int i=0;i<=2;i+)            cout<<"Input x="     cin>>x;       cout<<"sgn("<<x<<")="<<sgn(x)<<endl;    &

74、#160;   return 0; 【案例3-5】编写最值函数函数原型声明#include<iostream>using namespace std;/函数原型声明语句也可以在这里int main()         float max(float,float);                   

75、60;        /max()函数原型声明语句    float a,b,Max;                                  

76、60;   /变量声明语句    cout<<" Input a="    cin>>a;              /输入参数a    cout<<" Input b="    cin>>b;   &

77、#160;         /输入参数b    Max=max(a,b);                                 /调用max()函数 

78、0;   cout<<"max("<<a<<","<<b<<")="<<Max<<endl;    return 0;float max(float x,float y)     float z;    z=(x>y)?x:y;        return(z); &#

79、160;                                         /返回值类型为浮点型  【案例3-6】值传递和引用传递的区别#include <iostream>

80、 using namespace std;void fun(int,int&);                             /函数参数一个为值传递，一个引用传递int main()     int a = 22, b = 44;    cout &

81、lt;< "Initial a = " << a << ", b = " << b << endl;    fun(a,b);    cout << "After fun(a,b), a = " << a << ", b = " << b << endl;    fun(2*a-3,b);   

82、cout << "After fun(2*a-3,b), a = " << a << ", b = " << b << endl;    return 0;void fun(int x, int& y)     x = 88;  y = 99; 【案例3-7】编写最值函数内联函数#include<iostream>using namespace std;inline int max(int x,i

83、nt y)                  /使用inline关键字声明max()为内联函数    return x>y?x:y; int main()        int a=3,b=5,c;    c=max(a,b);    cout<<"max("&

84、lt;<a<<","<<b<<")="<<c<<endl;    cout<<"max("<<15<<","<<11<<")="<<max(15,11)<<endl;    return 0;        &

85、#160;           /计算面积和周长 【案例3-9】最小公倍数函数函数的嵌套调用#include <iostream>  using namespace std;long int gcd(long int m,long int n)                  

86、0;           /求最大公约数     if (m < n) swap(m,n); while (n>0)                    int r = m%n; m = n;   n = r;  &

87、#160;           return m;long int lcm(long int m,long int n)                            /求最小公倍数    return

88、 m*n/gcd(m,n); int main()     int m, n;    cout << "Please input two integers: " cin >> m >> n;    cout << "lcm(" << m << "," << n << ") = " << lcm(m,n

89、) << endl;    return 0; 【案例3-10】显示函数的参数带默认参数的函数#include <iostream>using namespace std;void disp(int x=1,int y=1,int z=1)                         /带有默认参数值

90、的函数       cout<<"Parameter 1 is: "<<x<<endl;    cout<<"Parameter 2 is: "<<y<<endl;    cout<<"Parameter 3 is: "<<z<<endl;int main()      

91、                                 /main()函数中测试参数带有默认值的函数disp()     cout<<"No actual parameter"<<endl;

92、60;   disp();    cout<<"One actual parameter"<<endl;    disp(1);    cout<<"Two actual parameter"<<endl;    disp(1,2);    cout<<"Three actual parameter"<

93、<endl;    disp(1,2,3);    return 0; 【案例3-11】通用最值函数参数数目可变的函数#include <iostream>#include <cstdarg>using namespace std;int max(int,int.);                   &#

94、160;            /原型声明int main()      int a,b,c,d,e;    cout<<"Enter five integers, seperate with space:" cin>>a>>b>>c>>d>>e;    cout<<"The

95、 maxmum in a and b is:"<<max(2,a,b)<<endl;    cout<<"The maxmum in five integers is:"<<max(5,a,b,c,d,e)<<endl;    return 0;int max(int num,int integer.)             

96、/定义参数数目可变的函数     va_list ap;     int n=integer;    va_start(ap,integer);    for(int i=1;i<num;i+)     int t=va_arg(ap,int); if(t>n)            n=t;&#

97、160;       va_end(ap);    return n;【案例3-12】多变的最值函数参数数目不同的重载函数#include <iostream>using namespace std;int main()     int min (int a, int b, int c);               

98、;         /函数声明    int min (int a, int b);                                /函数声明    in

99、t i1 ,i2,i3,i;    cout<<"Enter three integers:" cin >>i1 >>i2 >>i3;                    /输入3个整数    i = min(i1 ,i2) ;  cout <<"

100、The min in two intergers=" <<i <<endl;     / 2个整数中最小者    i = min(i1 ,i2 ,i3) ;                            &#

101、160;    / 3个整数中最小者    cout <<"The min in three intergers=" <<i <<endl;    return 0;int min(int a,int b,int c)                    

102、60;        /定义求3个整数中的最小者的函数     int k;      k=(a<b)?a:b;    k=(k<c)?k:c;    return k;int min(int a,int b)              

103、                      /定义求2个整数中的最小者的函数     int k;    k=(a<b)?a:b;    return k; 【案例3-13】求绝对值使用系统函数#include <iostream>#include <cmath&g

104、t;#include <cstdlib>using namespace std;void main( void )     int     ix = -4, iy;    long    lx = -41567L, ly;    double  dx = -3.141593, dy;    iy = abs( ix );   cout<<&qu

105、ot;The absolute value of"<<ix <<" is "<<iy<<endl;    ly = labs( lx );   cout<<"The absolute value of"<<lx <<" is "<<ly<<endl;    dy = fabs( dx );   cout<<&

106、quot;The absolute value of"<<dx <<" is "<<dy<<endl; 【案例3-14】将整数和小数分离使用系统函数#include<iostream>#include<cmath>using namespace std;void main(void)     double fraction, integer,number = 103.567;    fraction = modf(

107、number, &integer);    cout<<number<<"整数部分为:"<<integer<<" 小数部分为:"<<fraction; 【案例3-15】求平方根使用系统函数#include <iostream>#include <cmath>#include <cstdlib>using namespace std;void main( void )    

108、 double question = 45.35, answer;    answer = sqrt( question );    if( question < 0 )       cout<<"Error: sqrt returns "<<answer<<endl;    else       cout<<&q

109、uot;The square root of "<<question<<" is "<<answer<<endl; 【案例3-16】求随机数使用系统函数#include <iostream>#include <cstdlib>#include <ctime>using namespace std;void main(void)     cout << "RAND_MAX=" << RAND_MAX << endl;    cout<<"产生10个 0 到 99的随机数如下:n&q