如何获取字符串向量中的某个元素的位置，使用它作为ints向量中的索引？ [英] How to get position of a certain element in strings vector, to use it as an index in ints vector?

问题描述

我试图在 strings 的向量中获取元素的索引，以将其用作 int 类型，这是否可能？

I am trying to get the index of an element in a vector of strings, to use it as an index in another vector of int type, is this possible ?

示例：

vector <string> Names;
vector <int> Numbers;

 ... 
// condition to check whether the name exists or not
if((find(Names.begin(), Names.end(), old_name_)) != Names.end())  
    {   // if yes
        cout <<"Enter the new name."<< endl;
        cin >> name;
        replace(Names.begin(), Names.end(), old_name_, name);
    }

现在我想得到 old_name 向量中使用它来访问 Numbers 向量中的某个元素。所以我可以这样说：

Now I want to get the position of old_name in the Names vector, to use it in accessing certain element in Numbers vector. So that I can say:

Numbers[position] = 3 ; // or whatever value assigned here.

我尝试使用：

vector <string> :: const_iterator pos;
pos = (find(Names.begin(), Names.end(), old_name_))
Numbers[pos] = 3;

但显然这不起作用，因为 pos 是类型字符串！

but obviously this doesn't work since pos is of type string !

推荐答案

为了获得元素在向量中的位置，知道迭代器指向元素，从迭代器中减去 v.begin（）：

To get a position of an element in a vector knowing an iterator pointing to the element, simply subtract v.begin() from the iterator:

int pos = find(Names.begin(), Names.end(), old_name_) - Names.begin();

现在您需要检查 pos code> Names.size（）以查看它是否超出范围：

Now you need to check pos against Names.size() to see if it is out of bounds or not:

if(pos >= Names.size()) {
    //old_name_ not found
}

向量迭代器的行为方式类似于数组指针;大多数你知道的指针算术也可以应用于向量迭代器。从C ++ 11开始，您可以使用 std :: distance 代替迭代器和指针的减法。

Vector iterators behave in ways similar to array pointers; most of what you know about pointer arithmetic can be applied to vector iterators as well. Starting with C++11 you can use std::distance in place of subtraction for both iterators and pointers.

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