Check if a word from one text file is in a second text file (C++)

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I've got two text files: The first has ~100,000 words and the other has ~850,000 words. Both have been parsed into separate Vectors. If a word is in both files, I need to do something.

I've written some C++ code that loops through the first and the second file, but the time complexity is O(n^2) which with files this big is taking forever to run through. Even after 15 minutes it doesn't seem close to being finished.

for (string word1 : firstTextFile)
            {
                for (string word2 : secondTextFile)
                {
                    if (word1 == word2)
                    {
                        doSomething();
                    }
                }
            }

Is there a faster way to do this? I've searched everywhere but I've got no idea what to do. Any help would be great, thanks!

Short answer: yes.

The std::set_intersection function handles this case in linear time. If you are able to, simply use that.

(reference)

C# Read every second word from txt file, I want to believe that spaces separate words in your text file. You can do it like so: text.Split(' ')[1]. If there are many lines in your text file, you can loop through  First you have to extract a word from your text file. Second compare it with the word you want to search. true?-->found! false?-->extract the next word from the file and compare again etc. until the end of file is reached.

#include <algorithm>

for (string word1 : firstTextFile) {
  if (std::binary_search(secondTextFile.begin(), secondTextFile.end(), word1) {
    doSomething();
  }
}

Complexity above is O(firstTextFile.size() * log(secondTextFile.size()).

If you would use std::unoredered_set<std::string> secondTextFile instead of std::vector<std::string> secondTextFile:

for (string word1 : firstTextFile) {
  if (secondTextFile.count(word1)) {
    doSomething();
  }
}

Complexity is O(firstTextFile.size()).

Additionally you would save time on inserting and sorting words into secondTextFile: O(secondTextFile.size()) instead of O(secondTextFile.size() * log(secondTextFile.size())).

C Tutorial – Searching for Strings in a Text File » CodingUnit , Now we know that we have to add two functions: Usage() and Search_in_File(). Let's start with the easiest one: void Usage(char *filename) { printf("Usage: %s <​file>  Hi All, I am trying to copy the contents of a file and then paste this content into a specific location within another file. I can copy the contents no problem using get-content and then paste the content using the set-content (which i know is not correct as this is overwriting the file) i need to just paste it into the other file after the last <location/> tag.

As both vectors have been sorted, then the algorithm to achieve this is akin to a merge sort.

There is a linear walk through the lists, with the algorithm trying to keep both lists at about the same part of the dictionary ordering.

while( worda && wordb ){
    if( worda == wordb ){
       DoSomething();
       worda = nextWordFromA();
       wordb = nextWordFromB();
    } else if ( worda < wordb ) {
       worda = nextWordFromA();
    } else {
       wordb = nextWordFromB();
    }
}

C Read Text File, In this tutorial, you will learn how to read text file line by line by using standard I/O functions Second, use the function fgets() to read text from the stream and store it as a string. so you can check the newline or EOF file character to read the whole line. if (fp == NULL){. printf("Could not open file %s",filename);. return 1;. }. So, really its all about reading the text file a char by char and differentiating words by space and new lines letters. Let’s have a go at it! #include <stdio.h> #include <stdlib.h> int main (int argc, char * argv []) { // This program reads a file from its arguments and prints a word by word.

Find word in a textfile - C++ Forum, "Write a modular program in C++ that search in a file strings with the The second error is when I start the program and he doesn't count the Try ifstream File(path.c_str()) or enable C++11 support in your tool chain to use as-is. 1 2 3 4 5 6, Write the path of the file. file.txt File found. Write the word you 're  You could use something along these line : use While loop is used for reading one word at a time from the file till the end of file, strcmp will return 0, if word read by fscanf matches with word you want to search for. I haven’t tested it, but I think it should work. you can use the file function in c for file related operation.

C++ program to read file word by word, 1) Open the file which contains string. For example, file named “file.txt” contains a string “geeks for geeks”. 2) Create a filestream variable to store file content  If you want a quick solution choose this. words_dictionary.json contains all the words from words_alpha.txt as json format. If you are using Python, you can easily load this file and use as a dictionary for faster performance. All the words are assigned with 1 in the dictionary.

C program to Replace a word in a text by another given word , C program to Replace a word in a text by another given word. Given three strings 'str', 'oldW' and 'newW'. The task is find all occurrences of the word 'oldW' and replace then with word result = ( char *) malloc (i + cnt * (newWlen - oldWlen) + 1); Program to find second most frequent character · C Program to Sort an array​  Searching a specific string/word/etc in a text file? I am learning the joys of text file manipulation with C and having a blast However I am having issues trying to find information online on how to search (specifically a string in my case) in a text file.

Comments
  • Use the swiss army knife of algorithm design: Sort the data!
  • Both vectors have been sorted alphabetically with all duplicate words removed, it's still really slow!
  • Then you're doing it wrong: Linear search on a sorted vector. Anyhow, consider the first two elements: Either they are the same, or you can discard the lower one, because it can't possibly be matched. Also, there are other containers that offer faster lookup without additional programming on your side.
  • If you don't care about the order of the words, then you can use std::unordered_set which has a find() method of complexity O(1).
  • Both vectors have been sorted alphabetically with all duplicate words removed -- You must add this important information into you question!
  • But you need to sort both of the vectors, then +O(nlogn)
  • Please add explicitely that it's a solution for sorted vectors.