C++ vector::shrink_to_fit()用法及代碼示例

C++ 向量::shrink_to_fit() 函數

vector::shrink_to_fit() 是 "vector" header 的庫函數，用於減少容量以適應大小。詳細參考示例了解。

這可能會導致重新分配，但元素不會改變。

注意：要使用矢量，請包括<vector>標題。

vector::shrink_to_fit() 函數的語法

    vector::shrink_to_fit();

參數： none——它什麽都不接受。

返回值： void——它什麽都不返回。

例：

    Input:
    //capacity is initialized to be 100
    vector<int> arr(50); 
    arr.capacity() =50
    
    Resize:
    //doesn't change capacity though
    arr.resize(10); 
    arr.capacity() =50
    
    shrink_to_fit:
    //changes capacity as per resize, 
    //thus this practically reduced the capacity
    arr.shrink_to_fit();
    arr.capacity() =10

演示vector::shrink_to_fit()函數示例的C++程序

#include <iostream>
#include <vector>
using namespace std;

int main()
{
    vector<int> arr(50); //capacity is initialized to be 100
    cout << "...capacity of the vector:" << arr.capacity() << "...\n";

    arr.resize(10); //doesn't change capacity though
    cout << "...After resizing...\n";
    cout << "capacity of the vector:" << arr.capacity() << "\n";

    arr.shrink_to_fit(); //changes capacity as per resized vector
    cout << "...After using shrink_to_fit...\n";
    cout << "capacity of the vector:" << arr.capacity() << "\n";

    return 0;
}

輸出

...capacity of the vector:50... 
...After resizing... 
capacity of the vector:50 
...After using shrink_to_fit...
capacity of the vector:10 

參考：C++ 向量::shrink_to_fit()