CODEWITHSUNDEEP
c++stringfor-loopvectormax
user1026169
user1026169

Reputation: 5845

Using C++, trying to find the largest word in a vector using a for-loop and std::max

Using C++, I'm trying to put together a for loop that finds the largest word in a vector of strings. I know its possible to do this by comparing word lengths. So this is just wondering about some minutiae and learn a few things about C++, I can't figure out why this won't work:

#include <iostream>
#include <vector>
#include <algorithm>

int main() {
  std::string test = "this is a test string for sentence length ranks";
  std::vector<std::string> words = {"this", "is", "a", "test", "string", 
  "for", "sentence", "length", "ranks"};

  std::string temp = "";
  std::string largest = "";
  for (int i = 0; i != words.size(); ++i) {
    std::cout << "words[" << i << "]: " << words[i] << " "; 
    std:: cout << std::endl;
    temp = std::max(temp, words[i]);
    largest = std::max(temp, largest);
    std::cout << "the biggest word is " << largest << std::endl;
  }
return 0;
}

It returns this:

enter image description here

Update:

The answers here helped point me in the right direction. As it turns out there is another feature to std::max called 'comp'. I barely understand it, but this seems to work:

#include <iostream>
#include <vector>
#include <algorithm>

int main() {
  std::string test = "this is a test string for sentence length ranks";
  std::vector<std::string> words = {"this", "is", "a", "test", "string", 
  "for", "sentence", "length", "ranks"};

  std::string tempword;
  std::string longword;
  int longwordint = 0;
  for (int i = 0; i != words.size(); ++i) {
    int wordlength = words[i].length();
    longwordint = std::max(longwordint, wordlength);

    tempword = words[i];
    longword = std::max(longword, tempword, 
              [](std::string longword, std::string tempword) 
              { return (longword.size() < tempword.size()); });

    std::cout << "the biggest word so far is " << longwordint;
    std::cout <<" letters long: " << longword;
    std::cout << " | the tempword is: " << tempword << std::endl;
  }
return 0;
}

enter image description here

Upvotes: 2

Views: 840

Answers (2)

Chris Dodd
Chris Dodd

Reputation: 126203

std::max compares things with a normal comparison, which for string, compares their dictionary order, not their length. So all the results in your loop are as expected.

Upvotes: 3

Villance
Villance

Reputation: 51

You can use std::max_element to find largest word in a vector string.

#include <iostream>
#include <vector>
#include <algorithm>

int main() {
  std::string test = "this is a test string for sentence length ranks";
  std::vector<std::string> words = {"this", "is", "a", "test", "string", 
  "for", "sentence", "length", "ranks"};

    auto largest = std::max_element(words.begin(), words.end(), [](const auto& s1, const auto& s2){
      return s1.size() < s2.size();
    });
    std::cout << "the biggest word is " << *largest << std::endl;

return 0;
}

Upvotes: 3

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