c++课后部分习题答案

1.☆口令验证:#include<iostream>using namespace std;int main(){char n[10];cout<<"请输入口令:"<<endl;cin>>n;for(int i=0;i<3;i++){if(strcmp(n,"welcome")==0){cout<<"口令输入正确!"<<endl;break;}else{if(i<2){cout<<"密码错误,请再输入口令:"<<endl;cin>>n;}elsecout<<"你是非法用户!"<<endl;}}return 0;}2．#include<iostream>using namespace std;int main(){int m[30];double sum=0;double average;int count=-1;cout<<"请输入要统计的正实数，负数表示结束:";do{count++;cin>>m[count]; 边输入边统计}while(m[count]>=0);for(int i=0;i<30;i++){if(m[i]>=0)sum=sum+m[i];}average=sum/count;cout<<"你输入了"<<count<<"个数"<<endl;cout<<"他们的平均值为:"<<average<<endl;return 0;}3．插入数组：#include<iostream>using namespace std;int main(){int m[5]={1,3,5,7,9};int a,j,i;cout<<"插入前的数组为:";for(i=0;i<5;i++)cout<<m[i]<<"\t";cout<<endl;cout<<"请输入要插入的数:";cin>>a;for(i=0;i<5;i++){if((a>m[i])&&(a<m[i+1])){for(j=4;j>=i;j--)m[j+1]=m[j];m[i+1]=a;}if(a<m[0]){for(j=4;j>=0;j--)m[j+1]=m[j];m[0]=a;}if(a>m[4]){m[5]=a;}}cout<<"插入a后的数组为:";for(i=0;i<6;i++)cout<<m[i]<<"\t";return 0;}4．删除数组#include<iostream>using namespace std;int main(){int m[5]={1,3,5,7,9};int a,j,i;cout<<"插入前的数组为:";for(i=0;i<5;i++)cout<<m[i]<<"\t";cout<<endl;cout<<"请输入要删除的数:";cin>>a;for(i=0;i<5;i++){if(m[i]==a){for(j=i;j<5;j++)m[j]=m[j+1];}}if(i>=5){cout<<"查无此数!"<<endl;cout<<"删除a后的数组为:";for(i=0;i<5;i++)cout<<m[i]<<"\t";}else{cout<<"删除a后的数组为:";for(i=0;i<4;i++)cout<<m[i]<<"\t";}return 0;}5．字符串复制：1.#include<iostream> #include<cstring> #include<cstring>using namespace std;int main(){int m=0;int i=0;char ch[61]="we are the best!";char a[61];cout<<"复制后字符串为:";while(ch[i]!='\0') 不可忘{a[i]=ch[i];i++;}a[i]='\0';cout<<a;return 0;}2.#include<iostream>#include<cstring>using namespace std;int main(){int m=0;char ch[61]="we are the best!";char a[61];cout<<"复制后字符串为:";for(int i=0;i<strlen(ch);i++){a[i]=ch[i];}return 0;}6．进制转化：#include<iostream>#include<cmath>using namespace std;int main(){int a;int b[10];cout<<"请输入一个整数:";cin>>a;int i=0;while(a!=0){b[i]=a%2;a=a/2;i++;}cout<<"转化为二进制输出为:";for(i--;i>=0;i--)cout<<b[i];cout<<endl;return 0;}6．打印金字塔#include<iostream>using namespace std;void draw(int n){int i,j;for(i=0;i<n;i++){for(j=0;j<2*n-1;j++){if((j<n+i)&&(j>=n-i-1)){cout<<char('A'+i+j-5);}elsecout<<' ';}}}int main(){int n;cout<<"请输入n:";cin>>n;draw(n);return 0;}7．计算多项式值：#include<iostream>using namespace std;int power(int i,int k){int j;int result=1;for(j=1;j<=k;j++){result=result*i;return result;}int sumfac(int k,int i){int j;int result=1;for(j=1;j<=i;j++)result=result*k;return result;}int sum(int k,int n){int i;int sum=0;for(i=1;i<=n;i++)sum=sum+power(i,k)+sumfac(k,i);return sum;}int main(){int k,n;cout<<"请输入k,n的值:";cin>>k>>n;cout<<"多项式结果:"<<sum(k,n)<<endl;return 0;}8．置零：#include<iostream>using namespace std;int main(){int m[9]={10,20,30,40,50,60,70,80,90};int i,j;cout<<"请输入n:";cin>>i;int *ptr=m;for(j=0;j<i;j++)m[j]=0;cout<<"置零后的数组为:";for(j=0;j<9;j++){cout<<*(ptr+j)<<"\t";}return 0;}9．字符串反转：#include<iostream>#include<cstring>using namespace std;void mystrrev(char*string){int i;char n[20];int len=strlen(string);for(i=0;i<=len;i++)n[len-i]=*(string+i);for(i=0;i<=len;i++)cout<<n[i];}int main(){char m[20];cout<<"请输入待反转的字符串:";cin>>m;char*ptr=m;cout<<"反转后的字符串为:";mystrrev(m);return 0;}10．比较字符串：#include<iostream>#include<cstring>using namespace std;int mystrnicmp(char*str1,char*str2,int n){int i,j;for(i=0;i<n;i++){if(strcmp(str1,str2)<0)j=-1;if(strcmp(str1,str2)==0)j=0;if(strcmp(str1,str2)>0)j=1;}return j;}int main(){char m[]="competition";char a[]="cooperation";int n;char*str1=m;char*str2=a;cout<<"请输入n:";cin>>n;cout<<"比较结果为:"<<mystrnicmp(str1,str2,n)<<endl;return 0;}☆☆☆11．去处空格：#include<iostream>#include<cstring>using namespace std;char*mytrim(char*string){char*p=string;int len=strlen(string);char*ptr=string+len-1;int i=0;while(*ptr==' '){*ptr='\0';ptr--;}while(*ptr!=*p)ptr--;return ptr;}int main(){char str[]="who is buddha? ";cout<<"截取前字符串为:["<<str<<']'<<endl;cout<<"截取后的字符串为:["<<mytrim(str)<<']'<<endl;return 0;}7．查找字符串：#include<iostream>using namespace std;char*mystrchr(char*string,char c){int i;int len=strlen(string);for(i=0;i<len;i++){if(*(string+i)==c)return string+i;}if(i>=len)return NULL;}int main(){char m[]="hello world!";char*string=m;char c;cout<<"请输入要查找的字符串:";cin>>c;cout<<"该字符位置为:"<<mystrchr(string,c)<<endl;return 0;}13．电话本：#include<iostream>#include<cstring>using namespace std;struct P erson{char name[10];int number;};int main(){int i;const int count=5;Person person[count];char name;int number;cout<<"请输入5个人的信息:"<<endl;for(i=0;i<5;i++){cin>>person[i].name;cin>>person[i].number;}Person tmp;for(i=0;i<5;i++){for(int j=4;j>i;j--) /必须有/{if(strcmp(person[j].name,person[j-1].name)<0){tmp=person[j];person[j]=person[j-1]; /不可加name，注意[]/person[j-1]=tmp;}}}cout<<"按字典顺序排序:"<<endl;for(i=0;i<5;i++){cout<<person[i].name<<"\t"<<person[i].number<<endl;}char m[10];cout<<"请输入待查找的名字:";cin>>m;for(i=0;i<5;i++){if(strcmp(person[i].name,m)==0){cout<<person[i].name<<"\t"<<person[i].number<<endl;break;elsecout<<"查无此人!"<<endl;}return 0;}14.查找数组最值：#include<iostream>using namespace std;void result(int a[],int i,int&max_r,int&min_r){int j;max_r=a[0];min_r=a[0]; /不可缺少，否则无法正确输出最小值for(j=0;j<i;j++){if(max_r<a[j]) 注意引用max_r=a[j];}for(j=0;j<i;j++){if(min_r>a[j])min_r=a[j];}}int main(){int a[10];int max,min;cout<<"请输入一组数:";for(int i=0;i<5;i++) 输入一组数cin>>a[i];result(a,5,max,min);cout<<"该组元素最大值和最小值为:";cout<<max<<" "<<min<<endl;return 0;}15.构造猫类：#include<iostream>using namespace std;class cat{char Name[20];char Sex[20];int Weight;public:cat(char*name,char*sex,int age,int weight){strcpy(Name,name);strcpy(Sex,sex);Age=age;Weight=weight;cout<<"构造函数被调用!"<<endl; 易疏漏}~cat(){cout<<"析构函数被调用!"<<endl;}void display(){cout<<Name<<"\t"<<Sex<<"\t"<<Age<<"\t"<<Weight<<endl; 用大写字母}};int main(){cout<<"第一只猫:"<<endl;cat cat1("mimi","female",5,10);cat1.display(); 调用函数时注意cout<<"第二只猫:"<<endl;cat cat2("huahua","male",6,14);cat2.display();return 0;}16.地址类：#include<iostream>using namespace std;class address{char Name[20];char Street[20];char City[20];int Postcode;public:void set(char*name1,char*street,char*city,int postcode){strcpy(Name,name1);strcpy(Street,street);strcpy(City,city);Postcode=postcode;}void changename(char*name2){strcpy(Name,name2);}void display(){cout<<Name<<'\t'<<Street<<'\t'<<City<<'\t'<<Postcode<<endl;}};int main(){char name1[20],street[20],city[20],name2[20];int postcode;address address1;cout<<"please input the first address:";cin>>name1>>street>>city>>postcode;address1.set(name1,street,city,postcode); 不可少address1.display();cout<<"please input the changename:";cin>>name2;address1.changename(name2);address1.display();return 0;}17.圆类：#include<iostream>using namespace std;class point{int x;int y;public:void set(int a,int b){x=a; set不可忘y=b;}int getx(){return x;}int gety(){return y;}void display(){cout<<'['<<x<<","<<y<<']'<<endl;}};class circle{point center;double radius;public:void setcenter(point p){ 必须这样输，不可center=p; void setcenter(int a,int b) } x=a;y=b;void setradius(double r){radius=r;}double getradius(){return radius;}point getcenter(){ set后再get;get目的是取返回值return center;}double area(){return 3.14159*radius*radius;}double circumference(){return 2*3.14159*radius;}void display(){cout<<"center=";center.display();cout<<";radius="<<radius<<endl;}};int main(){int a,b,r;point center;circle c1;cout<<"请输入圆心点:";cin>>a>>b;center.set(a,b); 先调用point类cout<<"请输入半径:";cin>>r;c1.setcenter(center); 再调用circle类c1.setradius(r);c1.display();cout<<"该圆的面积为:"<<c1.area()<<endl;cout<<"该圆的周长为:"<<c1.circumference()<<endl;return 0;}18.汽车类:#include<iostream>using namespace std;class vehicle{public:int Speed; 必须全部设置为public,否则派生类无法调用double Weight;void set(int speed,double weight){Speed=speed;Weight=weight;}void display(){cout<<"最大时速:"<<Speed<<"\t"<<"车体重量:"<<Weight<<endl;}};class truck:public vehicle …:‟注意{double Load;double weight;public:void settru(int speed,double weight,double load){set(speed,weight);Load=load;}double ratio(){return Load/(Load+Weight);}void displaytru(){cout<<"最大载重:"<<Load;display();}};int main(){int speed;double weight,load;cout<<"请输入最高时速，车重，载重:";cin>>speed>>weight>>load;truck tru1;tru1.settru(speed,weight,load);tru1.displaytru();cout<<"载重效率为:"<<tru1.ratio()<<endl;return 0;}当机器提示出现无法访问私有函数时,可以将私有函数公有化.19.数据总分和平均分:#include<iostream>using namespace std;class total_ave{int array[5],total;double ave;public:void get_array(){total=0;cout<<"请输入5个数据:"<<endl;for(int i=0;i<5;i++){cin>>array[i];total=total+array[i];}ave=total/5;}void display(){cout<<"总分为:"<<total<<endl;cout<<"平均值为:"<<ave<<endl;}};int main(){total_ave array;total_ave*p;p=&array;p->get_array(); 必须使用指针,注意“->”p->display();return 0;}20.时间类:#include<iostream>#include<cmath>using namespace std;class time{int hour,minute,second;public:time(int h=0,int m=0,int s=0);void settime(int h=0,int m=0,int s=0);void display();int seccalc();time operator+(time&); 注意格式time operator-(time&);};time::time(int h,int m,int s){settime(h,m,s);}void time::settime(int hh,int mm,int ss){hour=(hh>23||hh<0)?0:hh;minute=(mm>60||mm<0)?0:mm;second=(ss>60||ss<0)?0:ss;}void time::display(){cout<<((hour<10)?"0":"")<<hour<<":"<<((minute<10)?"0":"")<<minute<<":"<<((second<10 )?"0":"")<<second<<endl; 注意表示方法，括号不可省，hour,second,minute不可省}int time::seccalc(){return hour*3600+minute*60+second; 为计算时间差,和准备}time time::operator+(time&t) 注意格式,不要输错operator {time tmp; 注意设置tmp;int ss;ss=seccalc()+t.seccalc();tmp.hour=ss/3600%24;tmp.minute=ss%3600/60;tmp.second=ss%3600%60;注意小时,分钟,秒钟的表示return tmp; 注意返回值}time time::operator-(time&t){time tmp;int ss;ss=abs(seccalc()-t.seccalc()); 注意设置绝对值tmp.hour=ss/3600%24;tmp.minute=ss%3600/60;tmp.second=ss%3600%60;return tmp;}int main(){time t1(1,13,25),t2,t3;t2.settime(23,18,45);cout<<"t1:";t1.display();cout<<"t2:";t2.display();t3=t1-t2;cout<<"t1-t2:";t3.display();t3=t1+t2;cout<<"t1+t2:";t3.display();return 0;}**21.文件的统计:#include<iostream>#include<fstream>using namespace std;int main(){ofstream outfile("a1.txt");if(!outfile){cout<<"文件打开失败!"<<endl;return 1;}outfile<<"I like visual c++!"<<endl;outfile.close();ifstream infile("a1.txt");if(!infile){cout<<"文件打开失败!"<<endl;return 0;}char ch;int count=0;int sum=1;while(!infile.eof()){infile.get(ch);count++;if(ch==' ')sum++;}cout<<"文件总长度为:"<<count<<endl; 为什么总长度多2 cout<<"单次个数为:"<<sum<<endl;infile.close();return 0;}22．不同域宽：#include<iostream>#include<iomanip>using namespace std;int main(){int a=12345;double b=1.2345;cout<<"按不同的精度打印:"<<endl;for(int i=0;i<11;i++){cout<<setw(i)<<a<<endl;cout<<setw(i)<<b<<endl;}return 0;}23.表示字符：#include<iostream>using namespace std;int main(){for(int i=33;i<127;i++){cout<<"十进制输出为:"<<dec<<i<<endl;cout<<"八进制输出为:"<<oct<<i<<endl;cout<<"十六进制输出为:"<<hex<<i<<endl;cout<<"字符输出为:"<<char(i)<<endl;}return 0;}24.进制转化：#include<iostream>#include<fstream>using namespace std;int main(){ofstream outfile("abc.txt");int a;cout<<"请输入一个十进制数:";cin>>a;if(!outfile){cout<<"文件打开失败!"<<endl;return 1;}outfile<<"十六进制为:"<<hex<<a<<"\t";outfile<<"八进制为:"<<oct<<a<<endl;outfile.close();return 0;}25.统计非负数：#include<iostream>#include<fstream>using namespace std;int main(){ofstream outfile("sum.txt");int m[10];int sum=0;int i;cout<<"请输入十个数:"<<endl;if(!outfile){cout<<"文件打开失败!"<<endl;return 1;}for(i=0;i<10;i++){cin>>m[i];}for(i=0;i<10;i++){if(m[i]>=0){cout<<"非负数为:"<<m[i]<<" ";outfile<<"非负数为:"<<m[i]<<" ";sum=sum+m[i];}}cout<<"非负数之和为:"<<sum<<endl;outfile<<"非负数之和为:"<<sum<<endl;outfile.close();return 0;}23．打印杨辉三角：#include<iostream>#include<fstream>using namespace std;int main(){ofstream outfile("report.txt");if(!outfile){cout<<"文件打开失败!"<<endl;return 1;}int m[20][20];int i,j,n;cout<<"please input the integer:"<<endl;for(i=0;i<10;i++){m[i][0]=1;m[i][i]=1;}for(i=2;i<10;i++){for(j=1;j<i;j++)m[i][j]=m[i-1][j-1]+m[i-1][j];}for(i=0;i<10;i++){for(j=0;j<=i;j++){cout<<m[i][j]<<"\t";outfile<<m[i][j]<<"\t";}cout<<endl;outfile<<endl;}outfile.close();return 0;}27分解输出：#include<iostream>#include<cmath>using namespace std;int main(){int m,t,a;cout<<"请输入一个数:";cin>>m;for(t=0;t<5;t++){if(m/pow(1000,t)==0)break;}a=t-3;int n[20];int i=0;int *ptr=n;while(n[i]!=0){n[i]=m%1000;m=m/1000;i++;if(i>a)break;}for(int j=i-1;j>=0;j--){cout<<*(ptr+j)<<",";}return 0;}如出现数据比较高时用字符数组输出。