习题答案目录：https://www.cnblogs.com/Mered1th/p/10485695.html
第6章 函数
练习6.4
#include<iostream>
using namespace std;
int fact(int x) {
if (x == 1) return x;
else return x * fact(x - 1);
}
int main() {
int x;
cout << "Please input a number:\n";
while (cin >> x) {
int ans = fact(x);
cout << ans << endl;
}
system("pause");
return 0;
}
练习6.5
#include<iostream>
using namespace std;
int abs(int x) {
return x >= 0 ? x : (-x);
}
int main() {
int x;
cout << "Please input a number:\n";
while (cin >> x) {
cout << abs(x) << endl;
}
system("pause");
return 0;
}
练习6.7
size_t count_calls(){
static size_t ctr=0;
return ctr++;
}
练习6.10
#include<iostream>
using namespace std;
void swap(int *x, int *y) {
int temp = *x;
*x = *y;
*y = temp;
}
int main() {
int x, y;
cin >> x >> y;
cout << x << y << endl;
swap(x, y);
cout << x << y << endl;
system("pause");
return 0;
}
练习6.12
void swap(int &x, int &y) {
int temp = x;
x = y;
y = temp;
}
练习6.17
不相同，因为转大写需要修改传入的字符串需要加&
#include<iostream>
#include<cctype>
#include<string>
using namespace std;
bool is_upper(const string s) {
for (auto i : s) {
if (isupper(i)) return true;
}
return false;
}
void to_upper(string &s) {
for (auto &i : s) {
i = toupper(i);
}
}
int main() {
string s = "abdcedA";
if (is_upper(s)) cout << "is upper" << endl;
else cout << "Not upper" << endl;
to_upper(s);
cout << s << endl;
system("pause");
return 0;
}
练习6.18
bool compare(matrix &a, matrix &b);
vector<int>::iterator change_val(int a, vector<int>::iterator);
练习6.19
a.不合法
b.合法
c.合法
d.合法
练习6.21
#include<iostream>
#include<cctype>
#include<string>
#include<vector>
using namespace std;
int Big(int x, int *y) {
return x > *y ? x : *y;
}
int main() {
int x = 3, y = 2;
cout << Big(x, &y) << endl;
system("pause");
return 0;
}
练习6.22
函数传参必须加引用，不加结果不正确。
#include<iostream>
#include<cctype>
#include<string>
#include<vector>
using namespace std;
void swap(int *&x, int *&y) {
int *temp = x;
x = y;
y = temp;
}
int main() {
int x = 3, y = 2;
int *px = &x, *py = &y;
swap(px, py);
cout << x << ", " << y << endl;
cout << *px << ", " << *py << endl;
system("pause");
return 0;
}
6.23
#include<iostream>
using namespace std;
void print(const int *pi) {
cout << *pi << endl;
}
void print(const int *beg, const int *end) {
while (beg != end) {
cout << *beg++ << " ";
}
cout << endl;
}
void print(const int ia[], size_t size) {
for (size_t i = 0;i != size;i++) {
cout << ia[i] << " ";
}
cout << endl;
}
void print2(const int (&arr)[2]) {
for (size_t i = 0;i != 2;i++) {
cout << arr[i] << " ";
}
cout << endl;
}
int main() {
int i = 0, j[2] = { 0,1 };
print(&i);
print(begin(j), end(j));
print(j, 2);
print2(j);
system("pause");
return 0;
}
练习6.24
如果数组大小小于10，会造成数组越界。除此以外数组不能复制成形参。改成指针或引用。
练习6.25
用命令行当做输入，输入的argv[0]保存程序的名字，后面的才是实参
#include<iostream>
#include<string>
using namespace std;
int main(int argc,char const **argv)
{
cout << argv[1] << endl;
cout << argv[2] << endl;
cout << string(argv[1])+string(argv[2]) << endl;
system("pause");
return 0;
}
练习6.26
#include<iostream>
#include<string>
using namespace std;
int main(int argc,char const **argv)
{
for (int i = 0;i < argc;i++) {
cout << argv[i] << endl;
}
system("pause");
return 0;
}
练习6.27
#include<iostream>
#include<string>
#include<initializer_list>
using namespace std;
int count_Sum(initializer_list<int> il) {
int sum = 0;
for (auto beg = il.begin();beg != il.end();beg++) {
sum += *beg;
}
return sum;
}
int main(int argc,char const **argv)
{
cout << count_Sum({ 1,2,3,4,5 }) << endl;
system("pause");
return 0;
}
练习6.28
string类型
练习6.29
如果实参个数多且占用容量大，用引用更好。
练习6.31
返回的引用是局部对象的引用时无效；返回的常量引用是局部常量对象的引用时。
练习6.32
合法，将数组重置为0-9
练习6.33
#include<iostream>
#include<string>
#include<vector>
using namespace std;
void print(vector<int>::iterator vec_begin, vector<int>::iterator vec_end) {
if (vec_begin != vec_end) {
cout << *vec_begin << " ";
return print(++vec_begin, vec_end);
}
}
int main(int argc,char const **argv)
{
vector<int> vec = { 1,2,3,4,6 };
print(vec.begin(), vec.end());
system("pause");
return 0;
}
练习6.34
如果传入的参数小于0，会一直调用不停止
练习6.35
会一直调用本身，无限循环
练习6.36
string (&fun(int i)[10];
练习6.39
a.合法
b.不合法
c.合法
练习6.40
a.正确
b.错误，一旦某个形参被赋予了默认值，它后面的所有形参都必须有默认值
练习6.41
a.非法，第一个形参没有默认值，必须给实参
b.合法
c.合法，'*'转换为整形
练习6.42
#include<iostream>
#include<string>
#include<vector>
using namespace std;
string make_plural(size_t ctr, const string &word, const string &ending = "s") {
return (ctr > 1) ? word + ending : word;
}
int main()
{
cout << make_plural(2, "success", "es") << endl;
cout << make_plural(2, "failure") << endl;
system("pause");
return 0;
}
练习6.43
a.放在头文件中，内联函数在程序中多个定义必须完全一致。
b.放在头文件中，函数声明。
练习6.44
#include<iostream>
#include<string>
#include<vector>
using namespace std;
inline bool isShorter(const string &s1, const string &s2) {
return s1.size() < s2.size();
}
int main()
{
string s1 = "abc", s2 = "abcd";
cout << isShorter(s1, s2) << endl;
system("pause");
return 0;
}
练习6.46
不能，返回值不是常量表达式
练习6.47
在项目属性中设置命令行/DNDEBUG就不会出现 #ifndef....#endif、assert中的内容。
#include<iostream>
#include<string>
#include<vector>
#include<cassert>
using namespace std;
void read_vi(vector<int>::const_iterator iterator_begin, vector<int>::const_iterator iterator_end) {
#ifndef NDEBUG
cerr << iterator_end - iterator_begin << __func__ << " " << __FILE__ << " "
<< __LINE__ << " " << __TIME__ << " " << __DATE__ << endl;
#endif // !NDEBUG
if (iterator_begin != iterator_end) {
cout << *iterator_begin << " ";
return read_vi(++iterator_begin, iterator_end);
}
else {
cout << endl;
return;
}
}
int main()
{
vector<int> v{ 1,2,3,4,5 };
read_vi(v.begin(), v.end());
system("pause");
return 0;
}
练习6.48
合理，输入结束时终止程序
练习6.50
a.非法，二义性
b.匹配void f(int)
c.匹配void f(int,int)
d.匹配void f(double,double)
练习6.53
a.合法
b.合法
c.不合法，重复定义
#include<iostream>
#include<string>
#include<vector>
using namespace std;
int calc(int&, int&);
int calc(const int&, const int&);
char calc2(char*, char*);
char calc2(const char*, const char*);
int calc3(char*, char*);
int calc3(char* const, char* const);
int main()
{
calc(1, 2);
system("pause");
return 0;
}
int calc(int&a, int&b) {
return a + b;
}
int calc(const int&a, const int&b) {
return a + b;
}
char calc2(char *a, char *b) {
return *a;
}
char calc2(const char *a, const char *b) {
return *a;
}
int calc3(char *a, char *b) {
return a - b;
}
int calc3(char* const a, char* const b) {
return a - b;
}
练习6.54
vector<int(*)(int, int)> vf;
练习6.55
#include<iostream>
#include<string>
#include<vector>
using namespace std;
int add(int a, int b) {
return a + b;
}
int sub(int a, int b) {
return a - b;
}
int multi(int a, int b) {
return a * b;
}
int divide(int a, int b) {
return a / b;
}
int main()
{
vector<int(*)(int, int)> vf{ add,sub,multi,divide };
for (const auto e : vf) cout << e(4, 2) << endl;
system("pause");
return 0;
}