如何从文本文件中搜索字符串答案

【问题标题】：How to search for a string from a text file如何从文本文件中搜索字符串
【发布时间】：2014-04-29 09:35:58
【问题描述】：

首先，这是我到目前为止的代码：

#include <iostream>
#include <string>
#include <fstream>

using namespace std;

int arraysize = 35;
int i = 0;
string line;
string searchTerm;

int main()
{
    string words[arraysize];
    ifstream wordFile;
    wordFile.open ("wordFile.txt");
    if (wordFile.is_open())
    {
        while (! wordFile.eof())
        {
            getline (wordFile, line);
            words[i] = line;
            i++;
        }
        wordFile.close();
    }
    else
    {
        cout << "Unable to open file" << endl;
    }

    for (int x = 0; x < arraysize; x++)
    {
        cout << words[x] << " ";
    }

    cout << "\n\nEnter in a word you would like to search in the story above:" << endl;
    cin >> searchTerm;

    for (int y = 0; y < arraysize; y++)
    {
        if (words[y].compare(searchTerm) !=0)
        {
            cout << "No match found" << endl;
        }
    }
}

到目前为止，我所拥有的是从文本文件读取然后打印这些单词的程序。我接下来要做的是让用户输入他们想在文本文件中搜索的单词，如果有像他们输入的单词一样的单词，如果没有打印出“没有单词”，则打印该单词就像在文本文件中一样” 我只是无法弄清楚搜索，关于如何做到这一点的任何建议？

【问题讨论】：

标签： c++ arrays string file search

【解决方案1】：

这是一个如何在字符串中搜索字符串的示例

// string::find
#include <iostream>       // std::cout
#include <string>         // std::string

int main ()
{
  std::string str ("There are two needles in this haystack with needles.");
  std::string str2 ("needle");

  // different member versions of find in the same order as above:
  std::size_t found = str.find(str2);
  if (found!=std::string::npos)
    std::cout << "first 'needle' found at: " << found << '\n';

  found=str.find("needles are small",found+1,6);
  if (found!=std::string::npos)
    std::cout << "second 'needle' found at: " << found << '\n';

  found=str.find("haystack");
  if (found!=std::string::npos)
    std::cout << "'haystack' also found at: " << found << '\n';

  found=str.find('.');
  if (found!=std::string::npos)
    std::cout << "Period found at: " << found << '\n';

  // let's replace the first needle:
  str.replace(str.find(str2),str2.length(),"preposition");
  std::cout << str << '\n';

  return 0;
}

这应该可以帮助您准确了解您需要做什么

注意参数 pos 如何用于搜索相同搜索字符串的第二个实例。 输出：

first 'needle' found at: 14
second 'needle' found at: 44
'haystack' also found at: 30
Period found at: 51
There are two prepositions in this haystack with needles.

【讨论】：

【解决方案2】：

怎么样：

int found = -1;
for (int y = 0; y < arraysize; y++)
{
    if (words[y].compare(searchTerm) ==0)
    {
        found = y;
        break;
    }
}

if ( found != -1 )
   cout << "found!" << endl;
else
   cout << "No match found" << endl;

或更短：

if ( std::find(std::begin(words), std::end(words), searchTerm) == std::end(words) )
  cout << "not found";
else
  cout << "found";

【讨论】：