C++重学（6）——string容器

本质：类

和char* 的区别：string内部有个char*，并且封装了很多方法

迭代器类型：随机迭代器（可用于标准算法、支持[]访问、-n、比较大小）

	string str;
	const char* ch = "hello";
	string str2(ch);
	cout << "str2 = " << str2 << endl;

	string str3(str2);
	cout << "str3 = " << str3 << endl;

	string str4(5,'a');
	cout << "str4 = " << str4 << endl;

	//string& operator=(const char* s)	char*类型字符串赋值给当前字符串
	string str1;
	str1 = "hello";
	cout << "str1 = " << str1 << endl;

	//string& operator=(char c)	字符赋值给当前字符串
	string str2;
	str2 = 'c';
	cout << "str2 = " << str2 << endl;

	//string& operator=(const string &s)	把字符串s赋值给当前的字符串
	string str3;
	str3 = str2;
	cout << "str3 = " << str3 << endl;

	//string& assign(const char *s)	把字符串s赋值给当前的字符串
	string str4;
	str4.assign("hello");
	cout << "str4 = " << str4 << endl;

	//string& assign(const char *s, int n)	把字符串s的前n个字符赋值给当前的字符串
	string str5;
	str5.assign("hello world",8);
	cout << "str5 = " << str5 << endl;

	//string& assign(const string &s)	把字符串s赋值给当前的字符串
	string str6;
	str6.assign(str5);
	cout << "str6 = " << str6 << endl;

	//string& assign(int n, char c)	用n个字符c赋值给当前的字符串
	string str7;
	str7.assign(5,'a');
	cout << "str7 = " << str7 << endl;

	//string& operator+=(const char* str)	重载操作符 +=
	string str1;
	str1 += "hello";
	cout << "str1 = " << str1 << endl;

	//string & operator+=(const string &str)	重载操作符 +=
	string str2;
	str2 += str1;
	cout << "str2 = " << str2 << endl;

	//string & operator+=(char c)	重载操作符 +=
	string str3;
	str3 += 'x';
	cout << "str3 = " << str3 << endl;

	//string & append(const char *s)	把字符串s追加到字符串结尾
	string str4;
	str4.append("hello");
	cout << "str4 = " << str4 << endl;

	//string& append(const char *s, int n)	把字符串s的前n个字符追加到字符串结尾
	string str5;
	str5.append("hello world",8);
	cout << "str5 = " << str5 << endl;

	//string& append(const string &s)	同operator += (const string &str)
	string str6;
	str6.append(str5);
	cout << "str6 = " << str6 << endl;

	//string& append(const string &s, int pos, int n)	字符串s中从pos开始的n个字符追加到字符串结尾
	string str7;
	str7.append(str6,0,5);
	cout << "str7 = " << str7 << endl;

	string str("0123456789@qq.com");
	string PersonQQ = str.substr(0,str.find('@'));
	string Flag = str.substr(str.find('@') + 1, str.size());
	cout << "PersonQQ = " << PersonQQ << endl;
	cout << "Flag = " << Flag << endl;

	string str("0123456");
	//string& insert(int pos, const char* s);	插入字符串
	str.insert(6, "7");
	cout << "str " << str << endl;

	//string& insert(int pos, int n, char c);	在指定位置插入n个字符c
	str.insert(8, 3,'a');
	cout << "str " << str << endl;

	//string& erase(int pos, int n = npos);	删除从Pos开始的n个字符
	str.erase(9, 2);
	cout << "str " << str << endl;

记法：find是从左到右的查找，而rfind是从右到左的查找

	string str("01234567890");

	//int find(const string& str, int poS = 0)const;查找str第一次出现位置, 从pos开始查找
	string str1 = "9";
	int index1 = str.find(str1, 0);
	cout << " find : index1 = " << index1 << endl;
	int index11 = str.find(str1, 0);
	cout << "rfind : index1 = " << index11 << endl;

	//int find(const char* s, int pos = 0)const;查找s第一次出现位置, 从pos开始查找
	int index2 = str.find("9", 5);
	cout << " find : index2 = " << index2 << endl;
	int index22 = str.find(str1, 0);
	cout << "rfind : index2 = " << index22 << endl;

	//int find(const char* s, int pos, int n) const;从pos位置 查找 s的前n个字符 第一次位置
	int index3 = str.find("6789", 2, 1);
	cout << " find : index3 = " << index3 << endl;
	int index33 = str.rfind("6789", 9, 1);
	cout << "rfind : index3 = " << index33 << endl;

	//int find(const char c, int pos = 0)const;	查找字符c第一次出现位置
	int index4 = str.find('8', 0);
	cout << " find : index4 = " << index4 << endl;
	int index44 = str.rfind('8',9);
	cout << "rfind : index4 = " << index44 << endl;

原理 : 转成ASCII码进行比较的

返回值：

函数

注意：【】和at方法建议使用在数据的读取上而非存储！

string str1("hello");
	for (int i = 0; i < str1.size(); i++) 
	{
		cout << str1[i] << " ";
	}
	cout << endl;
	for (int i = 0; i < str1.size(); i++)
	{
		cout << str1.at(i) << " ";
	}
	cout << endl;
	str1[1] = 'w';
	str1.at(2) = 'h';
	cout << "str1 = " << str1 << endl;