string查找示例见下，代码见下，以及对应运行结果见下：

#include<iostream>

using namespace std;

int main() {

	// 1
	string s1 = "hellooooworld";
	cout << s1.find("oooo") << endl;

	// 2
	cout << (int)s1.find("oooo", 8) << endl;
	cout << s1.find("oooo", 4) << endl;

	// 3
	cout << s1.find('o') << endl;
	cout << s1.find('o', s1.find('o') + 1) << endl;

	// 4 从右向左查找
	cout << s1.rfind("oo") << endl; 



}

运行结果见下：

string数据替换，代码见下：

#include<iostream>

using namespace std;

int main() {

	// 1 
	string s1 = "hello woooorld";
	s1.replace(7, 5, "or"); // 代表从第七个元素开始，取五个字符，替换成对应字符
	cout << s1 << endl;

	// 2
	s1 = "hello woooorld";
	s1.replace(s1.begin()+7, s1.begin()+12, "or"); // 这个区间是左闭右开的，所以要到12
	cout << s1 << endl;

	// 3
	s1 = "hello woooorld";
	s1.replace(s1.begin() + 7, s1.begin() + 12, "or123edafsgsrg", 2); 
	cout << s1 << endl;

}

运行结果见下

string子串获取，代码见下：

#include<iostream>

using namespace std;

int main() {

	// 1 
	string s1 = "hello woooorld";
	string sub_s1 = s1.substr(7, 4);
	cout << sub_s1 << endl;

	// 2
	string s2 = "xiaoxiaode&&yikeshu";
	int pos = s2.find("&&");
	string s3 = s2.substr(0, pos);
	cout << s3 << endl;

}

运行结果见下