ca33a_demo_c++_新旧代码的兼容char数组与vector_string相互转换

 1 /*ca33a_demo_c++33_CppPrimer_新旧代码的兼容_txwtech
 2 旧代码：数组和c风格字符串
 3 新代码：vector和string
 4 相互转换：
 5 c风格字符串<- ->string
 6 数组<- ->vector
 7 
 8 C3867错误。
 9 https://docs.microsoft.com/zh-cn/cpp/error-messages/compiler-errors-2/compiler-error-c3867?f1url=https%3A%2F%2Fmsdn.microsoft.com%2Fquery%2Fdev15.query%3FappId%3DDev15IDEF1%26l%3DZH-CN%26k%3Dk(C3867)%26rd%3Dtrue&view=vs-2019
10 const char *str=st.c_str(); c_str后面的括号不要忘记写上
11 
12 */
13 
14 #include <iostream>
15 #include <string>
16 #include <vector>
17 using namespace std;
18 
19 int main()
20 {
21     string st("Hello World");
22     st = st + " bill";
23     cout <<"c++:string st: "<< st << endl;
24 
25     const char *str=st.c_str();//c++转c风格字符串,必须加上const,常字符指针
26     cout << "c风格*str: "<<str << endl;
27     //getchar();
28     const size_t arr_size = 6;
29     int int_arr[arr_size] = {0,1,2,3,4,5};
30     vector<int> ivec(int_arr, int_arr + arr_size);//数组转vector, int_arr默认指针指向第一个，int_arr + arr_size指向最后一个的后面 [ 开区间，保活。 ）闭区间不包括。前包后不包
31     cout << "间隔ivec:" << endl;
32     for (vector<int>::iterator itr = ivec.begin(); itr != ivec.end(); ++itr)
33     {
34         cout << *itr << endl;
35     }
36     cout << "间隔ivec2:" << endl;
37     vector<int> ivec2(int_arr+1,int_arr+4);//2,3,4的数据赋值到vector
38     for (vector<int>::iterator itr = ivec2.begin(); itr != ivec2.end(); ++itr)
39     {
40         cout << *itr << endl;
41     }
42 
43     return 0;
44 }

 1 /*ca33b_demo_c++_txwtech
 2 vector数据放入数组
 3 */
 4 #include <iostream>
 5 #include <string>
 6 #include <vector>
 7 
 8 using namespace std;
 9 
10 int main()
11 {
12     vector<int> ivec;
13     int ival;
14 
15     cout << "Enter number:(Ctrl+Z to end)" << endl;
16     while (cin >> ival)
17         ivec.push_back(ival);
18 
19     int *parr = new int[ivec.size()];//创建动态数组
20     size_t ix = 0;
21     for (vector<int>::iterator iter = ivec.begin(); iter != ivec.end(); ++iter, ++ix)
22         parr[ix] = *iter;//vector数据放入数组
23     for (ix = 0; ix < ivec.size(); ++ix)
24     {
25         cout <<"vector to 数组" <<*(parr + ix) << endl;
26     }
27     delete[] parr;
28     return 0;
29 }

 1 /*习题4.34—4.35—c++_txwtech
 2 1.读入一组string数据，放入vector
 3 3.vector字符串->字符指针数组,vector每个字符串--创建新的动态字符数组，
 4 4.vector字符串复制到字符数组
 5 5.字符数组放到动态字符指针数组里面
 6 //cin与getline方法，cin遇到空格就默认一个字符串，getline不识别空格，直到回车，默认一个字符串输入结束
 7 */
 8 #define _CRT_SECURE_NO_WARNINGS
 9 #include <iostream>
10 #include <string>
11 #include <vector>
12 
13 using namespace std;
14 
15 int main()
16 {
17     vector<string> svec;
18     string str;
19     cout << "enter strings: (ctrl+Z) to end" << endl;
20     //while (cin >> str) //cin与getline方法，cin遇到空格就默认一个字符串，getline不识别空格，直到回车，默认一个字符串输入结束
21     while (getline(cin, str))
22         svec.push_back(str);//1
23     //创建动态字符指针数组
24     //数组里面放的指针
25     char **parr = new char*[svec.size()];
26 
27     size_t ix= 0;
28     for (vector<string>::iterator iter = svec.begin(); iter != svec.end(); ++iter, ++ix)
29     {
30         char *p = new char[(*iter).size() + 1];//*iter指向的是一个字符串//3
31         strcpy(p,(*iter).c_str());//vector转c风格//4
32         parr[ix] = p;//动态字符数组赋值给字符指针//5
33     }
34     cout << "content of vector: " << endl;
35     for (vector<string>::iterator iter = svec.begin(); iter != svec.end(); ++iter)
36     {
37         cout << *iter << endl;
38     }
39     cout << "Content of charactor arrays: " << endl;
40     for (ix = 0; ix != svec.size(); ++ix)
41     {
42         cout << parr[ix] << endl;
43     }
44     //每个指针delete
45     for (ix = 0; ix != svec.size(); ++ix)
46     {
47         delete parr[ix];
48     }
49     delete[] parr;
50 
51         //getchar();
52     return 0;
53 }