string容器-构造函数

基本概念

string本质上是一个类
string类内部封装了很多成员方法，例如：查找find、拷贝copy，删除delete，替换replace，插入insert
string管理char*所分配的内存，不用担心复制越界和取值越界等，由类内部进行负责

string和char*的区别：

char*是指针
string是一个类，类内部封装了char*，管理这个字符串，是一个char*型的容器。

string构造函数

函数原型：

string(); //创建一个空的字符串，例如string str;
- string(const char* s); //使用字符指针s初始化
string(const string& str); //使用一个string对象初始化另一个string对象
string(int n, char c); //使用n个字符c初始化

#include <iostream>
#include <string>
using namespace std;

void test01(){
	string s1();		//创建一个空的字符串
	
	const char* st1 = "hello world";
	string s2(st1);		//使用字符串st1初始化s2
	
	const string& st2 = "world";
	string s3(st2);		//使用一个string对象初始化另一个string对象
	
	int n = 2;
	char c = 'x';
	string s4(n, c);
	
	cout << "s1 = " << s1 <<endl;
	cout << "s2 = " << s2 <<endl;
	cout << "s3 = " << s3 <<endl;
	cout << "s4 = " << s4 <<endl;
}
int main() {
	test01();
	return 0;
}

1 = 1
s2 = hello world
s3 = world
s4 = xx

string赋值操作

函数原型：

方式一： =

#include <iostream>
#include <string>
using namespace std;

void test01(){
	string str1;
	str1 = "hello world";
	cout << "str1 = " << str1 << endl;
	
	string str2;
	str2 = str1;
	cout << "str2 = " << str2 << endl;
	
	string str3;
	str3 = 'a';
	cout << "str3 = " << str3 << endl;
}
int main() {
	test01();
	return 0;
}

str1 = hello world
str2 = hello world
str3 = a

方式二： assign

#include <iostream>
#include <string>
using namespace std;

void test01(){
	string str4;
	str4.assign("hello C++");
	cout << "str4 = " << str4 << endl;

	string str5;
	str5.assign(str4);
	cout << "str5 = " << str5 << endl;
	
	string str6;
	str6.assign("hello C++", 5);
	cout << "str6 = " << str6 << endl;
	
	string str7;
	str7.assign(8, 'x');
	cout << "str7 = " << str7 << endl;
}
int main() {
	test01();
	return 0;
}

str4 = hello C++
str5 = hello C++
str6 = hello
str7 = xxxxxxxx

拼接

函数原型

方式一： +=（可追加字符、char*、string类型）

#include <iostream>
#include <string>
using namespace std;

void test01(){
	string str1 = "I love ";
	str1 += "game ";
	cout << "str1 = " << str1 << endl;
	
	str1 += 'a';
	cout << "str1 = " << str1 << endl;
	
	string str2 = "nd eating!";
	str1 += str2;
	cout << "str1 = " << str1 << endl;
}
int main() {
	test01();
	return 0;
}

str1 = I love game 
str1 = I love game a
str1 = I love game and eating!

方式二： append

#include <iostream>
#include <string>
using namespace std;

void test01(){
	string str1 = "I love ";
	str1.append("game");
	cout << "str1 = " << str1 << endl;
	
	str1.append(":DNF abcde", 4);
	cout << "str1 = " << str1 << endl;
	
	string str2 = " and WZRY!";
	str1.append(str2);
	cout << "str1 = " << str1 << endl;
	
	string str3 = "aaa nice! abcdef";
	str1.append(str3, 3, 6);
	cout << "str1 = " << str1 << endl;
}
int main() {
	test01();
	return 0;
}

str1 = I love game
str1 = I love game:DNF
str1 = I love game:DNF and WZRY!
str1 = I love game:DNF and WZRY! nice!

查找和替换

查找

find和rfind的区别

find从左往右找
rfind从右往左找

#include <iostream>
#include <string>
using namespace std;

void finde(int pos){
	if(pos == -1){
		cout << "未找到该元素" << endl;
	}else{
		cout << "该元素的位置是：" << pos << endl;
	}
}
void test01(){
	string str1 = "abcdefgcd";
	int pos1 = str1.find("cd");
	finde(pos1);
	
	string str2 = "abcfg";
	int pos2 = str2.find("cd");
	finde(pos2);

	pos1 = str1.rfind("cd");
	finde(pos1);
	
	pos2 = str2.rfind("cd");
	finde(pos2);
}

int main() {
	test01();
	return 0;
}

该元素的位置是：2
未找到该元素
该元素的位置是：7
未找到该元素

替换

#include <iostream>
#include <string>
using namespace std;

void test01(){
	string str1 = "abcdefgcd";
	str1.replace(3,2,"112");
	cout << str1 <<endl;
}

int main() {
	test01();
	return 0;
}