4-28打卡c++ string容器

 1 #include<iostream>
 2 #include<string>
 3 using namespace std;
 4 //assign
 5 void test01()
 6 {
 7     string str1;
 8     //截取三个字符
 9     str1.assign("hello,world", 3);
10     //从第三个字符开始截取4个字符
11     str1.assign("hello,world", 3, 4);
12     cout << str1;
13     cout << endl;
14     //同理append也是如此
15     cout << str1.append("hello,world", 5) << endl;
16     cout << str1.append("hello,world", 4, 5);
17 }
18 //repalce find rfind
19 void test02()
20 {
21     string str1 = "hello";
22     //从第一个字符开始替换两个字符，同时插入一个字符串
23     str1.replace(1, 2, "22222");
24     cout << str1 << endl;
25     str1 = "hello,world";
26     //返回元素下标位置，找不到返回-1
27     int pos = str1.find("l");
28     cout << "pos=" << pos << endl;
29     pos = str1.rfind('l');
30     cout << "pos=" << pos << endl;
31     cout << str1.rfind("wo");
32 }
33 //compare,insert size []
34 void test03()
35 {
36     //compare比较字符串的ASCII值之和相等返回0，大于返回1，小于返回-1
37     string str1 = "hello";
38     string str2 = "hello";
39     int res = str1.compare(str2);
40     cout << res << endl;
41     //insert插入,从下表为4的元素前插入
42     str1.insert(4, "5555");
43     cout << str1 << endl;
44     //size返回字符串元素个数 []取出str1中的元素
45     for (int i = 0; i < str1.size(); i++)
46     {
47         cout << str1[i];
48     }
49     cout << endl;
50     
51 }
52 //erase substr
53 void test04()
54 {
55     string str1 = "hello,world";
56     //从下标为5的元素开始删除n个元素
57     str1.erase(5, 2);
58     cout << str1 << endl;
59     string str2=str1.substr(0, 5);
60     //从下标为0的元素开始返回5个字符
61     cout << str2 << endl;
62 }
63 
64 int main()
65 {
66     /*test01();*/
67     /*test02();*/
68     /*test03();*/
69     test04();
70     return 0;
71 }