c++.primer.plus第五版第七章编程练习答案

// 1#include <iostream>#include <cmath>using namespace std;double get_harmonic_mean(double n1,double n2);void print_result(double result);bool is_zero(double num);int main(){    double num1 = 0,num2 = 0;    double result = 0;    while( cin >> num1 >> num2)    {       // cout<<num1<<" " <<num2<<endl;        if(is_zero(num1) || is_zero(num2))            break;        else        {            result = get_harmonic_mean(num1,num2);            print_result(result);        }    }    return 0;}bool is_zero(double num){    if(abs(num) <= 1e-15)        return true;    else        return false;}double get_harmonic_mean(double n1,double n2){    return 2.0 * n1 * n2 / (n1 + n2);}void print_result(double result){    cout << "The result is " << result << endl;}// 2#include <iostream>using namespace std;int main(){    double golf_score[10],temp;    int i;    for(i = 0;i < 10;i++)    {        cin >> temp;        if(!cin)         // bad input        {            cin.clear();            while(cin.get() != '\n')                continue;            break;        }        golf_score[i] = temp;    }    for(int k = 0;k < i;k++)        cout << "golf_score-" << k + 1 << " is " << golf_score[k] << endl;    double sum = 0,average = 0;    for(int j = 0;j < i;j++)        sum += golf_score[j];    average = sum / i;    cout << "The average is " << average << endl;    return 0;}#include <iostream>const int len = 10;using namespace std;int get_golf_score(double golf_score[],int len);void display_golf_score(double golf_score[],int real_len);double get_golf_score_average(double golf_score[],int real_len);int main(){    int real_len;    double golf_score[10],average_of_golf_score;    real_len = get_golf_score(golf_score,len);    display_golf_score(golf_score,real_len);    average_of_golf_score = get_golf_score_average(golf_score,real_len);    cout << "The average of the golf_score is " << average_of_golf_score << endl;    return 0;}int get_golf_score(double golf_score[],int len){    int i;    double temp;    for(i = 0;i < len;i++)    {        cin >> temp;        if(!cin)         // bad input        {            cin.clear();            while(cin.get() != '\n')                continue;            break;        }        golf_score[i] = temp;    }    return i;}void display_golf_score(double golf_score[],int real_len){    for(int k = 0;k < real_len;k++)        cout << "golf_score-" << k + 1 << " is " << golf_score[k] << endl;}double get_golf_score_average(double golf_score[],int real_len){    double sum = 0;    for(int j = 0;j < real_len;j++)        sum += golf_score[j];    return  sum / real_len;}// 3#include <iostream>using namespace std;struct box{    char maker[40];    float height;    float width;    float length;    float volume;};void display_info_of_box(box val);void set_volume_of_box(box * val);void display_and_set_volume(void (*fun1)(box),void (*fun2)(box *),box  val1,box * val2);int main(){    box stru1 = {"kane",12.21,12.21,12.21,12.21};//    // a//    display_info_of_box(stru1);//    // b//    set_volume_of_box(&stru1);//    cout << "The volume of the box is \t\t" << stru1.volume << endl;    // c    display_and_set_volume(display_info_of_box,set_volume_of_box,stru1,&stru1);    cout << "The volume of the box is \t" << stru1.volume << endl;    return 0;}void display_info_of_box(box val){    cout << "The information of the box structure is :\n";    cout << "val.maker is \t\t" << val.maker << endl;    cout << "val.height is \t\t" << val.height << endl;    cout << "val.width is \t\t" << val.width << endl;    cout << "val.length is \t\t" << val.length << endl;    cout << "val.volume is \t\t" << val.volume << endl;}void set_volume_of_box(box * val){    box * temp = val;    temp->volume = temp->height * temp->length * temp->width;}void display_and_set_volume(void (*fun1)(box),void (*fun2)(box*),box val1,box *val2){    fun1(val1);    fun2(val2);}// 7.4 lotto.cpp// lotto.cpp -- probability of winning#include <iostream>// Note: soome implementations require double instead of long doublelong double probability(unsigned numbers, unsigned picks);int main(){    using namespace std;    double total, choices;    cout << "Enter the total number of choices on the game card and\n"            "the number of picks allowed:\n"; while((cin >> total >> choices) && choices <= total) // 注意这种用法    {        cout << "You have one chance in ";        cout << probability(total, choices);            // compute the odds        cout << " of winning.\n";        cout << "Next two numbers (q to quit): ";    }    cout << "bye\n";    return 0;}// the following function calculates the probability of picking picks// numbers correctly from numbers choiceslong double probability(unsigned numbers,unsigned picks){    long double result = 1.0;           // here come some local variables    long double n;    unsigned p;    for(n = numbers, p = picks; p > 0; n--,p--)        result = result * n / p;    return result;}// 4        此题有疑问！！！没理解题什么意思！！！#include <iostream>using namespace std;long double probability(unsigned field_number,unsigned special_number,unsigned special_choice,unsigned all_choice);int main(){    int field_number = 47, special_number = 27,special_choice = 1,all_choice = 5;    cout << "The result is ";    cout << probability(field_number, special_number,special_choice,all_choice) << endl;            // compute the odds    return 0;}long double probability(unsigned field_number,unsigned special_number,unsigned special_choice,unsigned all_choice){    double special_result = 1.0,end_result = 1.0;    for(;special_choice > 0;special_choice--,special_number--)        special_result = special_result * special_choice / special_number;    cout << "The special_result is " << special_result << endl;    int temp = all_choice - special_choice;    for(;temp > 0;temp--,--field_number)        end_result = end_result * temp / field_number;    end_result *= special_result;    return end_result;}// 5#include <iostream>using namespace std;long long jchfun(int val);int main(){    int in_num;    long long result;    cout << "Please input the number of jc: ";    while(1)    {        cin >> in_num;        result = jchfun(in_num);        cout << "The result is " << result << endl;    }    return 0;}long long jchfun(int val){    long long result;    if(val > 0)        result = val * jchfun(val - 1);    else if(val == 0)        return 1;    return result;}// 6#include <iostream>using namespace std;int Fill_array(double *p,int len_max);void Show_array(double *p,int len);void Reverse_array(double *p,int len);int main(){    int len_max,len;    double *p = NULL;   cout << "Please input the length of the array: ";   cin >> len_max;   p = new double [len_max];   len = Fill_array(p,len_max);   Show_array(p,len);   Reverse_array(p,len);   Show_array(p,len);   delete [] p;    return 0;}int Fill_array(double * p,int len_max){    int n;    double temp;    for(n = 0;n < len_max;n++)    {        cin >> temp;        if(!cin)        {            cin.clear();            while(cin.get() != '\n')                continue;            break;        }        p[n] = temp;    }    return n;}void Show_array(double *p,int len){    cout << "The numbers of the array is :\n";    for(int i = 0;i < len;i++)        cout << p[i] << ' ';    cout << endl;}void Reverse_array(double *p,int len){    double temp;    for(int i = 0;i < len - 1;i++,len--)    {        temp = p[i];        p[i] = p[len - 1];        p[len - 1] = temp;    }}//-----------------------------------------------------------------------------------------------------------------------// 7.7 arrfun3.cpp// arrfun3.cpp -- array functions and const#include <iostream>const int Max = 5;// function prototypesint fill_array(double ar[],int limit);void show_array(const double ar[], int n);          // don't change datavoid revalue(double r,double ar[], int n);int main(){    using namespace std;    double properties[Max];    int size = fill_array(properties, Max);    show_array(properties,size);    cout << "Enter revaluation factor: ";    double factor;    cin >> factor;    revalue(factor,properties,size);    show_array(properties,size);    cout << "Done.\n";    return 0;}int fill_array(double ar[], int limit){    using namespace std;    double temp;    int i;    for(i = 0;i < limit; i++)    {        cout << "Enter value #" << (i + 1) << ": ";        cin >> temp;        if(!cin)                                // bad input        1--        {            cin.clear();                        //                  2--            while(cin.get() != '\n')            //                  3--                continue;            cout << "Bad input;input process terminated.\n";            break;        }        else if(temp < 0)            break;        ar[i] = temp;    }    return i;}// the following function can use, but not alter,// the array whose address is arvoid show_array(const double ar[], int n){    using namespace std;    for(int i = 0; i < n; i++)    {        cout << "Property #" << (i + 1) << ": $";        cout << ar[i] << endl;    }}// multiplies each element of ar[] by rvoid revalue(double r,double ar[], int n){    for(int i = 0; i < n; i++)        ar[i] *= r;}//------------------------------------------------------------------------------------------------------------------------------// 7#include <iostream>const int Max = 5;// function prototypesdouble *fill_array(double ar[],int limit);void show_array(const double ar[], double * end);          // don't change datavoid revalue(double r,double ar[], double * end);int main(){    using namespace std;    double properties[Max];    double *end = fill_array(properties, Max);    show_array(properties,end);    cout << "Enter revaluation factor: ";    double factor;    cin >> factor;    revalue(factor,properties,end);    show_array(properties,end);    cout << "Done.\n";    return 0;}double * fill_array(double ar[], int limit){    using namespace std;    double temp;    int i;    for(i = 0;i < limit; i++)    {        cout << "Enter value #" << (i + 1) << ": ";        cin >> temp;        if(!cin)                                // bad input        1--        {            cin.clear();                        //                  2--            while(cin.get() != '\n')            //                  3--                continue;            cout << "Bad input;input process terminated.\n";            break;        }        else if(temp < 0)            break;        ar[i] = temp;    }    return &(ar[i]);}// the following function can use, but not alter,// the array whose address is arvoid show_array(const double ar[], double *end){    using namespace std;    int i = 0;    for(const double *p = ar;p != end;p++,i++)    {        cout << "Property #" << (i + 1) << ": $";        cout << *p << endl;    }}// multiplies each element of ar[] by rvoid revalue(double r,double ar[], double * end){    for(double *p = ar;p != end;p++)        *p *= r;}// 8#include <iostream>#include <cstring>using namespace std;const int SLEN = 30;struct student {    char fullname[SLEN];    char hobby[SLEN];    int ooplevel;};int getinfo(student pa[],int n);void display1(student st);void display2(const student *ps);void display3(const student pa[],int n);int main(){    cout << "Enter class size: ";    int class_size;    cin >> class_size;    while(cin.get() != '\n')        continue;    student * ptr_stu = new student[class_size];    int entered = getinfo(ptr_stu,class_size);    for(int i = 0;i < entered;i++)    {        display1(ptr_stu[i]);        display2(&ptr_stu[i]);    }    display3(ptr_stu,entered);    delete [] ptr_stu;    cout << "Done\n";    return 0;}int getinfo(student pa[],int n){    char fullname_temp[SLEN];    char hobby_temp[SLEN];    int ooplevel_temp,i;    for( i = 0;i < n;i++)    {        cout << i + 1 << ": Please input the fullname:";        cin >> fullname_temp;        cin.get();        if(!cin)        {            cin.clear();            while(cin.get() != '\n')                continue;            break;        }        strcpy(pa[i].fullname,fullname_temp);        cout << i + 1 << ": Please input the hobby:";        cin >> hobby_temp;        cin.get();        if(!cin)        {            cin.clear();            while(cin.get() != '\n')                continue;            break;        }        strcpy(pa[i].hobby,hobby_temp);        cout << i + 1 << ": Please input the ooplevel:";        cin >> ooplevel_temp;        cin.get();        if(!cin)        {            cin.clear();            while(cin.get() != '\n')                continue;            break;        }        pa[i].ooplevel = ooplevel_temp;    }    return i;}void display1(student st){    cout << "st.fullname is\t" << st.fullname << endl;    cout << "st.hobby is\t" << st.hobby << endl;    cout << "st.ooplevel is\t" << st.ooplevel << endl;}void display2(const student *ps){    const student *st = ps;    cout << "st.fullname is\t" << st->fullname << endl;    cout << "st.hobby is\t" << st->hobby << endl;    cout << "st.ooplevel is\t" << st->ooplevel << endl;}void display3(const student pa[],int n){    for(int i = 0;i < n;i++)    {        cout << "st.fullname is\t" << pa[i].fullname << endl;        cout << "st.hobby is\t" << pa[i].hobby << endl;        cout << "st.ooplevel is\t" << pa[i].ooplevel << endl;    }}// 9    还有个数组指针的形式待写！！！----------------------------------------------------------------======||||||#include <iostream>using namespace std;double add(double x,double y);double subtract(double x,double y);double multiply(double x,double y);double divide(double x,double y);double calculate(double x,double y,double (*p)(double,double));int main(){    double x,y;    while(1)    {        cout << "Please ininput the x,y: ";        cin >> x >> y;        if(!cin)        {            cin.clear();            while(cin.get() != '\n')                continue;            break;        }        double add_result = calculate(x,y,add);        cout << "x + y = " << add_result << endl;        double subtract_result = calculate(x,y,subtract);        cout << "x - y = " << subtract_result << endl;        double  multiply_result = calculate(x,y,multiply);        cout << "x * y = " << multiply_result << endl;        double divide_result = calculate(x,y,divide);        cout << "x / y = " << divide_result << endl;    }    return 0;}double calculate(double x,double y,double (*p)(double,double)){    return p(x,y);}double add(double x,double y){    return (x + y);}double subtract(double x,double y){    return (x - y);}double multiply(double x,double y){    return (x * y);}double divide(double x,double y){    return (x / y);}