1 //string字符串查找和替换  比较  存取 修改单个字符 插入和删除  string字串
  2 #include <iostream>
  3 #include<string>
  4 
  5 using namespace std;
  6 //查找
  7 
  8 void test01()
  9 {
 10     string str1 = "abcdefg";
 11 
 12     int pos =str1.find("de");
 13 
 14     if (pos == -1)
 15     {
 16         cout << "没有找到<<endl;" <<endl;
 17     }
 18     else
 19     {
 20         cout << "找到字符串的位置，pos=" << pos << endl;
 21     }
 22 
 23     cout << "pos = " << pos << endl;
 24 
 25     //rfind 和 find 区别
 26     //rfind从右往左查找    find从左往右查找
 27     pos = str1.rfind("de");
 28     cout << "pos" << pos << endl;
 29 
 30 
 31 
 32 }
 33 
 34 //替换
 35 void test02()
 36 {
 37     string str1 = "abcdefg";
 38     
 39     //从1号位置起 3个字符 替换为“1111”
 40     str1.replace(1, 3, "2222");
 41     cout << "str1 = " << str1 << endl;
 42 }
 43 
 44 //比较 
 45  // = 0    >1    <-1
 46 void test03()
 47 {
 48     string str3 = "xhello";
 49     string str4 = "hellllo";
 50 
 51     if (str3.compare(str4) == 0)
 52     {
 53         cout << "str1等于 str2" << endl;
 54     }
 55     else if (str3.compare(str4) > 0)
 56     {
 57         cout << "str3 大于 str4 " << endl;
 58     }
 59     else
 60     {
 61         cout << "str3 小于 str4 " << endl;
 62     }
 63 
 64 }
 65 
 66 //string 字符存取
 67 void test04()
 68 {
 69     string str = "hello";
 70     //cout << "str = " << str << endl;
 71 
 72     //第一种通过[]访问单个字符
 73     for (int i = 0; i < str.size(); i++)
 74     {
 75         cout << str[i] << " ";
 76     }
 77     cout << endl;
 78 
 79     //第二种通过at访问单个字符
 80     for (int i = 0; i < str.size(); i++)
 81     {
 82         cout << str.at(i) << " ";
 83     }
 84     cout << endl;
 85 
 86     //修改单个字符
 87     str[0] = 'x';
 88     cout << "str = " << str << endl;
 89 
 90     str.at(1) = 'z';
 91     cout << "str = " << str << endl;
 92 
 93 }
 94 
 95 //string 插入和删除
 96 
 97 void test05()
 98 {
 99     string str8 = "hello";
100 
101     //插入
102     str8.insert(1, "111");
103     cout << "str8 = " << str8 << endl;
104 
105     //删除
106     str8.erase(1, 3);
107     cout << "str8 = " << str8 << endl;
108 
109 }
110 
111 //string 求字串
112 void test6()
113 {
114     string str = "ancdef";
115 
116     string subStr = str.substr(1, 3);
117 
118     cout << "subStr = " << subStr << endl;
119 }
120 
121 //使用操作
122 void test7()
123 {
124     string email = "zhangsan@qq.com";
125     //从邮件地址中 获取 用户信息
126 
127     int pos = email.find("@"); //8
128     cout << "emial pos = " << pos << endl;
129 
130     string userName = email.substr(0, pos);
131     cout << "userName = " << userName << endl;
132 }
133 
134 int main()
135 {
136     //test01();
137     //test02();
138     //test03();
139 
140     //test04();
141 
142     //test05();
143     //test6();
144     test7();
145 }