c++ - 如何从 vector 中提取第一个元素并在循环中将 vector 大小减少 1

Question

string line= "";
vector<string> tokens;
//populate the vector 'tokens'

//loop through vector 'tokens' until it becomes empty
{
    //extract out 'line' containing the first element of the vector.
    //reduce the size of 'tokens' by one through deleting the first element 
}
//use 'line' string one by one in the subsequent code 

假设“tokens”包含两个元素，例如

cat, dog, bull

在第一次迭代中，我想从 vector 中提取“猫”并将其大小减小 1。它现在将包含:

dog, bull

现在，我想在循环外的后续代码中使用这个提取的元素“cat”(存储在字符串“line”中)。下次我想选择“狗”并使 vector 仅包含

bull

.等等。提前感谢您的想法!

Answer 1

当为了清空容器而遍历容器时，只要容器不为空，就更容易简单地进行迭代。

#include <iostream>
#include <string>
#include <vector>

int main()
{
    std::vector<std::string> tokens = {"cat", "dog", "bull"};
    while(tokens.empty() == false)
    {
        // Extract the data from first element in the list
        auto line = std::move(tokens.front());

        // Pop the moved element from the vector
        tokens.erase(tokens.begin());

        // Do work with 'line'
        std::cout << line << '\n';
    }

    return 0;
}

也就是说，从 vector 的前面移除元素是非常低效的，因为所有后面的元素都必须向上移动。考虑从后面移除元素。