STL之string

c++ vector的用法

#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
void test01() {
	string s;
	s.assign("abcde", 4); //assign赋值进行截取个前
	cout << s << endl;
	char *p = (char*) "hello world";
	s.assign(p, 10);
	cout << s << endl;
	s.assign(s, 2, 5); //从第二个开始截取5个数。
	cout << s << endl;
	//s = s.substr(2,5); //从第几个开始截取几个数 和assign一样
	//cout << s;
}


void test02() {
	string s = "hello world";
	for (int i = 0; i < s.size(); ++i)
		cout << s.at(i) << " ";
	try {
		cout << s.at(100);//可以触发异常，不会报错，但是貌似没啥大用 
	}
	catch (out_of_range &e) {
		cout << "异常为" << e.what();
	}
	catch (...) {
		cout << "捕获到其他异常";
	}
}

void test03() {
	string s = "我";
	string s2 = "爱北京天安门";
	s.append(s2); //相当于 +=
	cout << s << endl;
	//find查找
	string s3 = "abcdefg";
	int pos = s3.find("bc");
	cout << pos << endl;
	pos = s3.find("bcf");
	cout << pos << endl;
	pos = s3.find("bc", 2);//可加参数，不加默认是0；
	cout << pos << endl;
	string s4 = "12345656";
	//int find(const char *s, int pos, int n) const;//从pos开始查找字符串s中前n个字符在当前串中的位置
	int pos2 = s4.rfind("56",s4.size()-1 -2,1);//从pos开始从后向前
	cout << pos2 << endl;
	//替换
	string s5 = "hello";
	s5.replace(1, 3, "1111");//从1开始的连续三个字符被替换成1111
	cout << s5;

}


void test04() {
	//(1)int compare(const basic_string& __str)
	//和str按字典序比较大小，若小于str返回小于0的值，若等于str返回0，若大于str返回大于0的值
	string a = "e";
	string b = "H";
	cout << a.compare(b);
	string s = "aZ";
	string s2 = "ab";
	cout << s.compare(s2);



	//(2)int compare(size_type __pos, size_type __n, const basic_string& __str)
	//从pos位置开始长度为n的子字符串和str按字典序比较大小，返回值同上
	s = "helloworld";
	s2 = "rle";
	cout << s.compare(7, 3, s2);

	//(3)int compare(size_type __pos1, size_type __n1, const basic_string& __str, size_type __pos2, size_type __n2)
	//从pos1位置开始长度为n1的子字符串和str从pos2位置开始长度为n2的子字符串按字典序比较大小，返回值同上
	cout << s.compare(7, 3, s2, 0, 3);
		
		
}

void test05() {
	string s1 ="37987244@qq.com";
	string s2 = s1.substr(0, s1.find("@"));
	cout << s2;
}

void test06() {
	string s1 = "hello";
	s1.insert(1, "111");
	cout << s1 << endl;
	s1.erase(1, 3);
	cout << s1 << endl;
}

void func(string p) {
	cout << p << endl;
}

void test07() {
	string s = "abc";
	char t[8] = "helloo";
	cout << t << endl;
	char *p = (char*)s.c_str();//c_str()生成一个const char*的指针
	cout << p<< endl;
	//func(s);//string 不能隐式转化为char *
	func(p);//char * 可以隐式转化为string
	string s2 = p;
	cout << s2;

}
void test08() {
	string s = "hello";
	char &a = s[2];
	char &b = s[3];
	a = '1';
	b = '2';
	cout << s << endl << (char*)s.c_str();
	s = "ppppp";
	cout << a << " " << b;//此时可以继续使用a,b；
	//s = "ppppppppppppppppppppp" 此时无法使用，因为编译器重新分配了一块内存；
}
int main()
{
	test08();
}