C++的vector类
用数组存放数据时，容量大小不可变，vector对象容量可自动增大。
vector的操作：
调用push_back函数时，vector对象的容量可能会增大。
观察下列操作对vector的影响：
#include <vector>
#include <iostream>
#include <string>#include "Helper.h"
int main()
{//用c++11的列表初始化，创建vector对象words1std::cout<< "用c++11的列表初始化，创建vector对象words1"<< std::endl;std::vector<std::string> words1{"Hello","World!","Welcome","To","C!"};PRINT(words1);std::cout << std::endl;//删除words1最后一个元素std::cout << "删除words1最后一个元素" << std::endl;words1.erase(words1.end()-1);PRINT(words1);//在words1尾部追加元素std::cout << "在words1尾部追加元素" << std::endl;words1.push_back("C++!");PRINT(words1);std::cout << std::endl;//用迭代器拷贝words1的内容以创建words2std::cout << "1、用迭代器拷贝words1的内容以创建words2" << std::endl;std::vector<std::string> words2(words1.begin()+2, words1.end());PRINT(words2);std::cout << std::endl;//在words中插入元素std::cout << "2、在words中插入元素" << std::endl;words2.insert(words2.begin(),"Hello!");PRINT(words2);std::cout << std::endl;//用拷贝构造创建words3std::cout << "3、用拷贝构造创建words3" << std::endl;std::vector<std::string> words3(words2);PRINT(words3);std::cout << std::endl;//用[]修改words的元素std::cout << "4、用[]修改words的元素" << std::endl;words3[3] = "C Plus Plus";PRINT(words3);std::cout << std::endl;//创建words4，初始化为多个相同的字串std::cout << "5、创建words4，初始化为多个相同的字串" << std::endl;std::vector<std::string> words4(4, "C++!");PRINT(words4);std::cout << std::endl;//words3与words4交换std::cout << "6、words3与words4交换" << std::endl;words3.swap(words4);PRINT(words3);PRINT(words4);std::cout << std::endl;return 0;
}
字符串字面量
C++11原始字符串字面量
语法: R “delimiter( raw_characters )delimiter”
“Raw String literals”在程序中写成什么样子，输出之后就是什么样子。我们不需要为“Raw String literals”中的换行、双引号等特殊字符进行转义。
#include <vector>#include <iostream>
const char* s1 = R"(Hello
World)";// s1效果与下面的s2和s3相同const char* s2 = "Hello\nWorld";const char* s3 = R"NoUse(Hello
World)NoUse";int main() {std::cout << s1 << std::endl;std::cout <<std::endl;std::cout << s2 << std::endl;std::cout << std::endl;std::cout << s3 << std::endl;}
C++14的字符串字面量
C++14将运算符 ""s 进行了重载，赋予了它新的含义，使得用这种运算符括起来的字符串字面量，自动变成了一个 std::string 类型的对象。
auto hello = "Hello!"s; // hello is of std::string type
auto hello = std::string{"Hello!"}; // equals to the above
auto hello = "Hello!"; // hello is of const char* type
已知’\0’在字符串里面代表结束符号
#include <string>
#include <iostream>
int main() {using namespace std::string_literals;std::string s1 = "abc\0\0def";std::string s2 = "abc\0\0def"s;std::cout << "s1: " << s1.size() << " \"" << s1 << "\"\n";std::cout << "s2: " << s2.size() << " \"" << s2 << "\"\n";
}
)
