如何在c ++中的字符串向量中使用find函数？ [英] How to use the find function in a string vector in c++?

问题描述

我在vector类中了解了find函数，我想尝试一下。事实是，当我使用单个单词并使用查找功能时，它可以完美地运行。但是当我在字符串向量中输入诸如This is a line之类的行，然后使用find函数来搜索诸如is之类的单词。它没有显示任何东西。我想知道如何解决这个问题。请帮帮我。

 vector< string> vec（ 0 ）; 
 vec.push_back（  Jack）; 
 vec.push_back（  12）; 
 vec.push_back（ 这是一行）; 
 
  if （std :: find（vec.begin（），vec.end（），  line）！= vec.end（）） //  这不起作用 
 {
 cout<<   vector有元素<< endl; 
} 

解决方案

这是 std :: find mehod，请参阅 std :: find at C ++ reference [ ^ ]。您需要编写其他代码才能找到包含搜索字符串作为子字符串的项目（可能是 std :: find_if [ ^ ]更符合您的需求。）




std :: find 匹配传递给函数的整个值，而不是它的一部分。在函数调用中，向量中的值不匹配行，因此您无法获得匹配。如果你想要一个匹配在子字符串上的find，你必须使用 std :: find_if ，它允许你传入谓词而不是使用的std :: string ::运算符==

I learnt about the find function in the vector class and i wanted to give it a try. The fact is that when i use single words and use the find function then it works perfectly. But when i enter a line such as "This is a line" in the string vector and then use the find function to search for a word such as "is". It doesnt show anything. I am wondering how to fix this issue. Please help me out.

vector<string> vec(0);
vec.push_back("Jack");
vec.push_back("12");
vec.push_back("This is a line");

if (std::find(vec.begin(), vec.end(), "line") != vec.end()) // this doesnt work
{
    cout<<"vector has the element"<<endl; 
}

解决方案

That is the correct behaviour of the std::find mehod, see std::find at C++ reference[^]. You need to write additional code in order to find items containing the search-string as substring (Possibly std::find_if[^] better fits your needs).

std::find matches the whole value you pass into the function, not a part of it. In your function call no value in your vector matches "line" so you don't get a match. If you want a find that matches on a substring you'll have to use std::find_if that enables you to pass in a predicate instead of using std::string::operator==.

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