#include<iostream> #include<cstring> #define N 100 using namespace std; class String{ public: String(const string&); void display() { cout<<Head<<endl; } void re(); ~String() { delete[] Head; } private: char *Head; }; String::String(const string &str) { Head = new char[100]; for(int i = 0; i != str.size(); ++i){ Head[i] = str[i]; } } void String::re() { for(int i = 0, j = strlen(Head) - 1; i < j; ++i, --j) { swap(Head[i], Head[j]); } } int main() { string str = "hi~"; String s(str); s.display(); s.re(); s.display(); return 0; }
一、动态分配内存。
1、像上面那样：a-动态分配，通常在构造器里完成。
char *Head;
Head = new char[100];
b-删除。
~String() { delete[] Head; }
越界访问的结果是未知的。
#include <iostream> #include <cstdio> #include <string> using namespace std; int main() { int n; cin >> n; int *a; a = new int[n]; printf("size of a=%d ", n); for (int i = 0; i != n; ++i) { a[i] = i; // 动态分配内存后表现得和数组一模一样~ cout << a[i] << endl; } // 表忘记删除 delete [] a; printf("delete a!"); return 0; }
2、还有个技巧就是用来重新初始化，
#include <iostream> #include <cstdio> #include <string> using namespace std; int main() { char *word; word = new char[100]; char c; int i = 0; cout << "Create word array and enter the words." << endl; while (cin >> c) { word[i++] = c; } cout << "word:" << word << ' '; delete [] word; cout << "Delete word:" << endl; cout << "word:" << word << ' '; return 0; }
char *word在c++中表现得和常量字符串是一样的。
Create word array and enter the words. ?@#!@#!@#!@# ^Z word:?@#!@#!@#!@# Delete word: word:
3、下面是二维数组的动态创建。参考博客 -> here
#include <iostream> #include <cstdio> #include <string> using namespace std; void create(int **&p, int row, int col) { p = new int*[row]; // p是一个指向、指向int的指针的、指针 for (int i = 0; i != row; ++i) p[i] = new int[col]; } void init(int **&p, int row, int col) { int k = 0; for (int i = 0; i != row; ++i) for (int j = 0; j != col; ++j) p[i][j] = k++; } void delt(int **&p, int row) { for (int i = 0; i != row; ++i) delete [] p[i]; delete [] p; } void print(int **&p, int row, int col) { for (int i = 0; i != row; ++i) { for (int j = 0; j != col; ++j) printf("%d ", p[i][j]); cout << endl; } } int main() { int row, col; int **p; // int* *p; cin >> row >> col; create(p, row, col); init(p, row, col); print(p, row, col); delt(p, row); return 0; } /* ps: 尝试使用range for: 失败 for (int x : p) { cout << p << " "; } */
二、把非模板类改成模板类。
。。Java里的对象只要需要就一直存在，而c++中的local对象的生命周期仅限花括号内，要接收函数内return的对象的那个对象所属的类必须实现了对应的拷贝方法。。。
参考这里 -> click here!
三、c++继承。（仿Java）
#include <iostream> #include <cstdio> #include <string> using namespace std; class Tool { private: int nl, np, nw; string fac; public: Tool(int nl, int np, int nw, string fac): nl(nl), np(np), nw(nw), fac(fac) { printf("Tool Constructor... "); } void display() { printf("tool[nl=%d,np=%d,nw=%d,fac=%s] ", nl, np, nw, fac); } }; class Motor : virtual public Tool { private: int nm; public: Motor(int nl, int np, int nw, int nm, string fac): Tool(nl, np, nw, fac), nm(nm) { printf("Motor Constructor... "); } void display() { Tool::display(); printf("motor[nm=%d] ", nm); } }; class Bicycle : virtual public Tool { private: int comp; public: Bicycle(int nl, int np, int nw, int comp, string fac): Tool(nl, np, nw, fac), comp(comp) { printf("Bicycle Constructor... "); } void display() { Tool::display(); printf("Bicycle[comp=%d] ", comp); } }; class motoBicycle : public Motor, public Bicycle { private: int price; public: motoBicycle(int nl, int np, int nw, int price, string fac): Tool(nl, np, nw, fac), Motor(nl, np, nw, 0,fac), Bicycle(nl, np, nw, 0,fac), price(price) { printf("motoBicycle Constructor... "); } void display() { Tool::display(); printf("motoBicycle[price=%d] ", price); } }; class Car : public Motor { private: int pov; public: Car(int nl, int np, int nw, int pov, string fac): Tool(nl, np, nw, fac), Motor(nl, np, nw, 0, fac), pov(pov) { printf("Car Constructor... "); } void display() { Motor::display(); printf("Car[pov=%d] ", pov); } }; class Truck : public Motor { private: int pov; public: Truck(int nl, int np, int nw, int pov, string fac): Tool(nl, np, nw, fac), Motor(nl, np, nw, 0, fac), pov(pov) { printf("Truck Constructor... "); } void display() { Motor::display(); printf("Truck[pov=%d] ", pov); } }; class Bus : public Motor { private: int pov; public: Bus(int nl, int np, int nw, int pov, string fac): Tool(nl, np, nw, fac), Motor(nl, np, nw, 0, fac), pov(pov) { printf("Bus Constructor... "); } void display() { Motor::display(); printf("Bus[pov=%d] ", pov); } }; int main() { Tool t(4, 4, 250, "myTool"); t.display(); Motor m(2, 2, 150, 100, "myMotor"); m.display(); Bicycle b(2, 2, 100, 2, "myBicycle"); b.display(); motoBicycle mb(2, 2, 100, 1700, "myMotoBicycle"); mb.display(); Car c(1, 2, 3, 4, "myCar"); c.display(); Truck tr(1, 2, 3, 4, "myCar"); tr.display(); Bus bu(1, 2, 3, 4, "myCar"); bu.display(); return 0; } 运行结果： Tool Constructor... tool[nl=4,np=4,nw=250,fac=L�] Tool Constructor... Motor Constructor... tool[nl=2,np=2,nw=150,fac=(�] motor[nm=100] Tool Constructor... Bicycle Constructor... tool[nl=2,np=2,nw=100,fac=�a] Bicycle[comp=2] Tool Constructor... Motor Constructor... Bicycle Constructor... motoBicycle Constructor... tool[nl=2,np=2,nw=100,fac=旋a] motoBicycle[price=1700] Tool Constructor... Motor Constructor... Car Constructor... tool[nl=1,np=2,nw=3,fac=橗a] motor[nm=0] Car[pov=4] Tool Constructor... Motor Constructor... Truck Constructor... tool[nl=1,np=2,nw=3,fac=h齛] motor[nm=0] Truck[pov=4] Tool Constructor... Motor Constructor... Bus Constructor... tool[nl=1,np=2,nw=3,fac=8齛] motor[nm=0] Bus[pov=4]
通过virtual解决二义性
q:子类访问父类的属性？