STL基本原理
案例一：构建一个简易容器
1 #include<iostream> 2 3 using namespace std; 4 5 //功能：查找一个容器中某元素个数 6 int _find(int* start, int* end, int num) 7 { 8 int count = 0; 9 while (start != end) 10 { 11 if (*start == num) 12 { 13 ++count; 14 } 15 ++start; 16 } 17 return count; 18 } 19 20 int main() 21 { 22 int _array[] = { 0,2,9,1,2,3,2 }; 23 /*int _array[6]; 24 int j = 0; 25 for (auto& _element:_array) 26 { 27 _element = j*j; 28 ++j; 29 } 30 int* end = &(_array[sizeof(_array)/sizeof(int) - 1]); 31 cout << "*end = " << *end << endl;*/ 32 33 int* _begin = _array;//指针指向首元素 34 int* _end = &(_array[sizeof(_array) / sizeof(int)]); 35 int count; 36 count = _find(_begin, _end, 2); 37 cout << "count = " << count << endl; 38 system("pause"); 39 return 1; 40 }
1 // string不同考虑越界问题，内存清理；所以在C++中建议你不要用char*，改用string 2 // string是一个类 3 4 #include<string> 5 #include<iostream> 6 7 using namespace std; 8 9 void test02() 10 { 11 cout << " test02()：" << endl; 12 string strA = "shiruiyu"; 13 string strB; 14 15 //成员函数 [] 遍历【越界不提醒！】 16 for (int i = 0; i < strA.size(); i++) 17 { 18 cout << strA[i]; 19 } 20 cout << endl; 21 // 操作符 at 遍历【越界抛出异常】 22 for (int i = 0; i < strA.size(); i++) 23 { 24 cout << strA.at(i); 25 } 26 cout << endl; 27 try 28 { 29 //cout << strA.at(10) << endl;//越界 抛出异常 打印 30 //cout << strA[10] << endl;//越界 不抛出异常 31 } 32 catch (const std::exception&) 33 { 34 cout << "越界！" << endl; 35 } 36 } 37 38 //重载符 39 void test04() 40 { 41 cout << " test04()：" << endl; 42 string s = "shi"; 43 string s2; 44 s += s; 45 cout << s << endl; // shishi 46 string s3 = "rui"; 47 s.append(s3); 48 cout << s << endl;// shishirui 49 50 string s4 = "12345"; 51 string s5 = "678"; 52 s4.append(s5, 2, 1);//一般前面表示起始下标，后面表示个数（包含起始位置） 53 cout << s4 << endl; // 123458 54 } 55 56 //查找 57 void test05() 58 { 59 cout << " test05()：" << endl; 60 string s = "123454321"; 61 int pos = s.find("3"); 62 cout << "第一次出现位置：pos = " << pos <<endl; 63 int _pos = s.find("5", 3);//4 64 int __pos = s.find("454", 0,2);//从 0开始查找 “454”的前2个字符“45”第一次出现的位置 65 int pos_ = s.rfind("3"); 66 cout << "最后一次出现位置：pos_ = " << pos_ << endl; 67 } 68 69 //替换 70 void test06() 71 { 72 cout << " test06()：" << endl; 73 string s = "shiruiyu"; 74 s.replace(0, 3, "zhang"); 75 cout << "s = " << s.c_str() << endl;//zhangruiyu 76 } 77 //比较 78 void test07() 79 { 80 cout << " test07()：" << endl; 81 string s1 = "abce"; 82 string s2 = "abcd"; 83 if (s1.compare(s2)== 0) 84 { 85 cout << "字符串相等！" << endl; 86 } 87 else if (s1.compare(s2) == 1) 88 { 89 cout << "s1 > s2" << endl; 90 } 91 else 92 { 93 cout << "s1 < s2" << endl; 94 } 95 } 96 // 子串操着 和 删除 97 void test08() 98 { 99 cout << " test08()：" << endl; 100 string s = "shiruiyu"; 101 //子串 102 string mysub = s.substr(1, 3); 103 cout << mysub.c_str() << endl; // hir 104 105 //删除 106 s.erase(0, 2);//一般前面表示起始下标，后面表示个数（包含起始位置） 107 cout << "删除前面两个s = " << s.c_str() << endl;// iruiyu 108 s.insert(2, "2222"); 109 cout << "插入到第2个元素前面s = " << s.c_str() << endl;// ir2222uiyu 110 } 111 112 int main() 113 { 114 test02(); 115 test04(); 116 test05(); 117 test06(); 118 test07(); 119 test08(); 120 return 1; 121 }
find的例子：
//代码来自 http://www.cplusplus.com/reference/string/string/find/ // 这个网站可以在线编译
1 // string::find 2 #include <iostream> // std::cout 3 #include <string> // std::string 4 5 int main() 6 { 7 std::string str("There are two needles in this haystack with needles."); 8 std::string str2("needle"); 9 10 // different member versions of find in the same order as above: 11 std::size_t found = str.find(str2); 12 if (found != std::string::npos) 13 std::cout << "first 'needle' found at: " << found << ' '; 14 //可用于重复查找 15 found = str.find("needles are small", found + 1, 6);// 从 found + 1 位置开始查找 needle 出现的位置 16 if (found != std::string::npos) 17 std::cout << "second 'needle' found at: " << found << ' '; 18 19 found = str.find("haystack"); 20 if (found != std::string::npos) 21 std::cout << "'haystack' also found at: " << found << ' '; 22 23 found = str.find('.'); 24 if (found != std::string::npos) 25 std::cout << "Period found at: " << found << ' '; 26 27 // let's replace the first needle: 28 str.replace(str.find(str2), str2.length(), "preposition");// 这个替换功能很有趣 29 std::cout << str << ' '; 30 31 return 0; 32 }
1 // string::find 2 #include <iostream> // std::cout 3 #include <string> // std::string 4 #include<algorithm> 5 #include<vector> 6 using namespace std; 7 int main() 8 { 9 std::string str("abc acc abc"); 10 // 查找某字符出现次数 11 // <1> 直接遍历 12 vector<int> positions; 13 for (int i = 0; i < str.size(); i++) 14 { 15 if (str[i] == 'b') 16 { 17 positions.push_back(i); 18 } 19 } 20 // <2> 利用find成员方法 21 vector<int> positions_; 22 std::size_t found = 0; 23 while (true) 24 { 25 found = str.find("c", found, 1); // 第二次从“ acc abc”查找；应为下面 found++ 26 if (found == std::string::npos) 27 { 28 break; 29 } 30 cout << "found = " << (found) << endl; 31 positions_.push_back(found); 32 found++; 33 } 34 35 36 return 0; 37 }
1 // 参考： http://www.cnblogs.com/Pillar/p/4206452.html 2 #include<string> 3 #include<iostream> 4 using namespace std; 5 6 int main() 7 { 8 char* chars = "shiruiyu"; //对于 sizeof(chars)/sizeof(char)) new 的时候 +1 //遍历的时候不用 9 // <1> char* 转 string 10 string string_ = chars;// 深度拷贝 11 chars = "hehe"; 12 cout << chars << endl; // hehe 13 cout << string_ << endl; // shiruiyu 14 // <2> string 转char* 15 const char* chars_ = new char[string_.size() + 1]; 16 string string__ = "china"; 17 chars_ = string__.data(); // 必须是const类型 18 cout << chars_ << endl; // china 19 return 1; 20 }
// string char* char 之间的转换
1 #include<iostream> 2 #include<string> 3 4 using namespace std; 5 6 int main() 7 { 8 string str1 = "shiruiyu"; 9 char* chars1 = new char[str1.size()]; // 接收string 10 // string 转 char* 11 strcpy(chars1, str1.c_str()); 12 cout << "chars1 = " << chars1 << endl; // char* 可以直接打印 13 // char* 转 string 14 string str2 = chars1; 15 16 // string 转 char 17 char chars2[] = ""; // 接收string 18 strcpy(chars2, str1.c_str()); 19 cout << "chars2 = " << chars2 << endl; 20 // char 转 string 21 string str3 = chars2; 22 return 1; 23 }
【问题：sizeof 与 length（string的成员函数） 区别？】
见我博客：https://www.cnblogs.com/winslam/p/9406330.html 【前几行】