C++的string

短命女 2022-06-13 06:13 138阅读 0赞

1.  C++中初始化string对象有这几种方式

*   *  string str; //这样初始化时，str为空字符
     *  string str = "bbb"; //将右边的字符串字面值赋值给str字段
     *  string str1("AAA"); //用字符串字面值初始化str1
     *  string str2(str1); //将str2初始化为str1的一个副本
     *  string str4(5,'a'); //结果为aaaaa，这样可以指定初始化成'a'字符的5个副本

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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50.031746031746025%"> string的常用操作</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:49.904761904761905%"> 说明</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.empty()</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 检查str是否是空字符串，若str为空字符串，则返回true,否则返回false</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.size()</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 返回str中字符的个数</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str[n]</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> string类型其实是一个char数组，所以可以用索引访问指定位置的字符，位置从0开始</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str+str1</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 字符串连接和C#一样，将两个字符串连接成新的字符串，返回新的字符串</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str = str1</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 字符串赋值操作</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str == str2</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 字符串比较相等</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str != str2</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 字符串比较不相等</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> string str = "hello"+"world" &nbsp; &nbsp;X</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 这样是不合法的，字符串的+号相连C++只允许和类型是string的字段相连接，不允许两个字符串字面值直接相连接</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.substr(1,5)</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 返回从str字符串中第1个位置开始，往后的5个字符组成的字符串,如果只填了位置参数，没有填个数的话，那么默认个数为填的位置参数后面的字符串长度，如果输入的位置参数超过了字符的长度，那么会抛出std::out_of_range的异常</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.insert(2,str1)</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 在指定位置插入字符串，例如在str字符串的第二个位置，插入str1的字符串</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.begin()</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 得到指向字符串开头的Iterator</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.end()</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 得到指向字符串结尾的Iterator</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.rbegin()</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 得到指向反向字符串开头的Iterator，也就是end</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.rend()</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 得到指向反向字符串结尾的Iterator，也就是begin</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.length()</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 和size的函数是一样的，得到的是字符串的大小</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.max_size()</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 字符串可能的最大大小</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.capacity()</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 在不重新分配内存的情况下，字符串容器的大小</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.append("aaa")</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 在字符串的末尾追加字符</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.erase()</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 删除字符串的内容</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.clear()</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 清空字符容器中所有内容，和erase函数不一样的是，这个函数返回的是void</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.replace(1,1,"L")</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 字符替换，例如从字符串str的第一个位置开始往后的1个字符，替换成'L'</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.copy()</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 字符串拷贝</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.find()</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 查找，返回基于0的索引号</td> 
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   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> str.rfind()</td> 
   <td style="border-style:solid; border-width:1px; border-color:rgb(211,211,211); padding:10px; margin:0px; width:50%"> 反向查找</td> 
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暂时只记录下目前用得到的字符串的函数，后面用到的其他的，再行补上

\#include <string>

\#include <iostream>

using namespace std;

int main(void)

string str = "abcdefg";

//str的第1个位置往后的5个字符组成的子字符串

string str1 = str.substr(1,5);

//结果：bcdef

cout << str1 << endl;

string str2 = "123";

//在str字符串的第2个位置插入str2字符串