C++ string中find ，rfind 等函数用法总结及示例

客官°小女子只卖身不卖艺 2022-03-17 01:21 355阅读 0赞

**string中 find()的应用 （rfind() 类似，只是从反向查找）**

**原型如下：**

**（1）size\_t find (const string& str, size\_t pos = 0) const; //查找对象--string类对象**

**（2）size\_t find (const char\* s, size\_t pos = 0) const; //查找对象--字符串**

**（3）size\_t find (const char\* s, size\_t pos, size\_t n) const; //查找对象--字符串的前n个字符**

**（4）size\_t find (char c, size\_t pos = 0) const; //查找对象--字符**

**结果：找到 -- 返回 第一个字符的索引**

**没找到--返回 string::npos**

**示例：**

#include <iostream>       // std::cout#include <string>         // std::stringint main (){  std::string str ("There are two needles in this haystack with needles.");  std::string str2 ("needle");  // different member versions of find in the same order as above:  std::size_t found = str.find(str2);  if (found!=std::string::npos)    std::cout << "first 'needle' found at: " << found << '\n';  found=str.find("needles are small",found+1,6);  if (found!=std::string::npos)    std::cout << "second 'needle' found at: " << found << '\n';  found=str.find("haystack");  if (found!=std::string::npos)    std::cout << "'haystack' also found at: " << found << '\n';  found=str.find('.');  if (found!=std::string::npos)    std::cout << "Period found at: " << found << '\n';  // let's replace the first needle:  str.replace(str.find(str2),str2.length(),"preposition");  //replace 用法  std::cout << str << '\n';  return 0;}

**结果：**

**first 'needle' found at: 14**

**second 'needle' found at: 44**

**'haystack' also found at: 30**

**Period found at: 51**

**There are two prepositions in this haystack with needles**

**其他还有 find\_first\_of(), find\_last\_of(), find\_first\_not\_of(), find\_last\_not\_of()**

**作用是查找 字符串中 任一个字符 满足的查找条件**

**string snake1("cobra");**

**int where = snake1.find\_first\_of("hark");**

**返回3 因为 "hark"中 各一个字符 在 snake1--cobra 中第一次出现的是 字符'r'（3为 cobra 中'r'的索引）**

**同理：**