Vector pop_back（）刪除多於1個條目

Question

我有一個簡單的函數，它在向量中仍存在元素時循環。在循環內部，使用pop_back（）從矢量的末尾彈出單個元素。由於某種原因，我的代碼每次調用時都會刪除2個元素。

vector<Vertex> vertices; 

while (vertices.size() != 0) { 
    std::cerr << "We are in the loop, size: " << vertices.size() << std::endl; 
    Vertex tmp = vertices.back(); 
    // do stuff with tmp, not shown here; 
    vertices.pop_back(); 
} 

輸出如下：

We are in the loop, size: 3 
We are in the loop, size: 1 

爲了澄清，這是上面的確切的代碼的輸出。

編輯：

vector<Vertex> vertices; 

while (vertices.size() != 0) { 

    Vertex tmp = vertices.back(); 
    std::cerr << "We are in the loop, size: " << vertices.size() << std::endl; 
    vertices.pop_back(); 
    std::cerr << "We are in the loop, size: " << vertices.size() << std::endl; 
} 

輸出：

We are in the loop, size: 3 
We are in the loop, size: 1 
We are in the loop, size: 1 
We are in the loop, size: 0 

編輯2：

我改變了我實現從向量雙端隊列。使用完全相同的命令，我設法實現所需的輸出：

We are in the loop, size: 3 
We are in the loop, size: 2 
We are in the loop, size: 2 
We are in the loop, size: 1 
We are in the loop, size: 1 
We are in the loop, size: 0 

仍然無法解釋之前的行爲;感謝大家的幫助。

Answer 1

由於Kerrek SB提到的錯誤是不是在給出的代碼，我試過下面的代碼，它工作正常。

#include <iostream> 
#include <vector> 

int main (int argc, char **argv) { 
    std::vector<int> v; 
    for (int i = 0; i < 10; i++) { 
     v.push_back(i); 
    } 
    while (!v.empty()) { 
     std::cerr << "We are in the loop, size: " << v.size() << std::endl; 
     int tmp = v.back(); 
     v.pop_back(); 
    } 
}