std::basic_string<CharT,Traits,Allocator>::shrink_to_fit

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< cpp‎ | string‎ | basic string
 
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basic_string::shrink_to_fit
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void shrink_to_fit();
 (C++11 起)
(C++20 前)
constexpr void shrink_to_fit();
 (C++20 起)

请求移除未使用的容量。

这是减少 capacity() 到 size() 的非强制请求。是否满足请求取依赖于实现。

若（且唯若）发生重分配，则非法化所有指针、引用和迭代器。

参数

（无）

返回值

（无）

复杂度

（未指明）

(C++17 前)

与 string 大小成线性

(C++17 起)

示例

运行此代码
#include <iostream>
#include <string>
 
int main()
{
    std::string s;
    std::cout << "Default-constructed capacity is " << s.capacity() 
        << " and size is " << s.size() << '\n';
    for (int i=0; i<42; i++)
        s.append(" 42 ");
    std::cout << "Capacity after a couple of appends is " << s.capacity() 
        << " and size is " << s.size() << '\n';
    s.clear();
    std::cout << "Capacity after clear() is " << s.capacity() 
        << " and size is " << s.size() << '\n';
    s.shrink_to_fit();
    std::cout << "Capacity after shrink_to_fit() is " << s.capacity() 
        << " and size is " << s.size() << '\n';
}

可能的输出： 

Default-constructed capacity is 15 and size 0
Capacity after a couple of appends is 240 and size 168
Capacity after clear() is 240 and size 0
Capacity after shrink_to_fit() is 15 and size 0

参阅

 返回字符数
(公开成员函数)
返回当前对象分配的存储空间能保存的字符数量
(公开成员函数)
来自“https://zh.cppreference.com/mwiki/index.php?title=cpp/string/basic_string/shrink_to_fit&oldid=64842”