C++ primer 第五版 第四章练习答案

4.6

#include "stdafx.h"#include<iostream>using namespace std;int main() {int a=0;cin >> a;if (a % 2 == 0) {cout << "偶数"<< endl;}else {cout << "奇数" << endl;}}

4.7

1----指针溢出

#include "stdafx.h"#include<iostream>#include<string>using namespace std;int main() {int a[3] = { 0,0,0 };for (auto q = a; q != a+5; ++q) {cout << *q << endl;}}

2----unsigned溢出

#include "stdafx.h"#include<iostream>#include<string>using namespace std;int main() {int a = 20;unsigned int b = a / -5;cout << b << endl;}

3----short溢出

#include "stdafx.h"#include<iostream>#include<string>using namespace std;int main() {short a = 32768;}

4.10

#include<iostream>using namespace std;int main() {int a = 0;while (cin>>a && a!=42) {cout << "yes" << endl;}}

4.11

#include<iostream>using namespace std;int main() {int a=5, b=4, c=3, d=2;if (a > b && b > c && c > d) {cout << "符合" << endl;}}

4.21

#include<iostream>using namespace std;int main() {int a=5, b=4, c=3, d=2;if (a > b && b > c && c > d) {cout << "符合" << endl;}}

4.22

1----使用多个if

#include<iostream>#include<vector>using std::vector;using namespace std;int main() {int grade;cin >> grade;if (grade >= 90) {cout << "high pass";}else {if (grade >= 75) {cout << "pass";}else {if (grade >= 60) {cout << "low pass";}else {cout << "fail";}}}}

2----只使用条件运算符

#include<iostream>#include<vector>using std::vector;using namespace std;int main() {int grade;cin >> grade;cout << ((grade >= 90) ? ("high pass") : (grade >= 75) ? ("pass") : (grade >= 60) ? ("low pass") : ("fail"));}

4.28

#include<iostream>using namespace std;int main() {cout << sizeof(bool) << endl;cout << sizeof(char) << endl;cout << sizeof(wchar_t) << endl;cout << sizeof(char16_t) << endl;cout << sizeof(float) << endl;cout << sizeof(double) << endl;cout << sizeof(long double) << endl;}

4.29

#include<iostream>using namespace std;int main() {int a[10]; int*p = a;cout << sizeof(a) / sizeof(*a) << endl;;cout << sizeof(p) / sizeof(*p);}

4.31

#include<iostream>using namespace std;#include<vector>int main() {vector<int>ivec = { 0,1,2 };vector<int>::size_type cnt = ivec.size();for (vector<int>::size_type ix = 0; ix != ivec.size();) {ivec[ix++] = cnt--;}for (auto q : ivec) {cout << q << endl;}}