删除向量中的字符串 [英] Delete strings in a vector

问题描述

我有一个充满字符串的向量

I have a vector full of strings

向量consistentWords包含4个字符串

the vector consistentWords contains 4 strings

1. def
2. edf
3. fedf
4. hedf

现在我想删除所有不以字母 d 开头的字符串

Now I want to delete all the strings that words don't start with the letter d

然而它最终只是删除了 eedf 和 hedf 而我留下的结果是

However it ends up just deleting eedf and hedf and the result I have left is

1. def
2. fedf

我的代码:

    for(int q=0; q<consistentWords.size(); q++)
    {
        string theCurrentWord = consistentWords[q];
        if(theCurrentWord[0] != 'd')
        {
            consistentWords.erase(consistentWords.begin()+q);
        }
    }

有什么想法吗?我只是不明白为什么不删除所有不以 d 开头的字符串.

Any thoughts? I just can't see why it's not deleting all of the strings that don't start with d.

推荐答案

问题是您在同一次迭代中从向量中删除元素并增加索引 q.所以在你的 for 循环的第二次迭代中，你从你的向量中删除 "eedf" 然后你的向量是 ["dedf", "fedf", "hedf"] 和q = 1.但是当您循环回到 for 循环的开头时，q 增加到 2，因此您接下来查看 "hedf"，跳过 "fedf".要解决此问题，您可以在从数组中删除元素时减少 q，如下所示:

The problem is you are deleting elements from the vector and incrementing your index q in the same iteration. So in the 2nd iteration of your for loop, you erase "eedf" from you vector then your vector is ["dedf", "fedf", "hedf"] and q = 1. But then when you loop back to the begining of the for loop, q is incremented to 2 so you look at "hedf" next, skipping "fedf". To fix this you could decrement q when you remove an element from the array like so:

for(int q=0; q<consistentWords.size(); q++)
{
    string theCurrentWord = consistentWords[q];
    if(theCurrentWord[0] != 'd')
    {
        consistentWords.erase(consistentWords.begin()+q);
        --q;
    }
}

或者你可以使用迭代器:

Or you could use iterators:

vector<string>::iterator it = consistentWords.begin()
while(it != consistentWord.end())
{
    string theCurrentWord = consistentWords[q];
    if(theCurrentWord[0] != 'd')
    {
        it = consistentWords.erase(it);
    }
    else
    {
        ++it;
    }
}

请注意，erase 会返回一个迭代器，指向您擦除的元素之后的元素.您必须重新分配 it 因为当向量调整大小时它变得无效.

Note that erase returns an iterator to the element after the one you have erased. You must re-assign it because it becomes invalidated when the vector is resized.

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