Problem 42 Coded triangle numbers（ifstream +getline）

小咪咪 2022-07-15 02:42 50阅读 0赞

## Coded triangle numbers ##

### Problem 42 ###

The *n*th term of the sequence of triangle numbers is given by, *tn* = ½*n*(*n*\+1); so the first ten triangle numbers are:

1, 3, 6, 10, 15, 21, 28, 36, 45, 55, ...

By converting each letter in a word to a number corresponding to its alphabetical position and adding these values we form a word value. For example, the word value for SKY is 19 + 11 + 25 = 55 = *t*10. If the word value is a triangle number then we shall call the word a triangle word.

Using [words.txt][] (right click and 'Save Link/Target As...'), a 16K text file containing nearly two-thousand common English words, how many are triangle words?

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         <span style="font-size:18px">Answer:</span> 
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       <td><strong><span style="font-size:18px">162</span></strong></td> 
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       <td colspan="2"><span style="color:rgb(153,153,153)"><span style="font-size:18px">Completed on Sun, 30 Oct 2016, 07:00</span></span></td> 
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题解：ifstream +getline ...

![20161030151934799][]

代码：

#include <iostream>
    #include <string>
    #include <fstream>
    #include <cmath>
    
    using namespace std;
    
    int wordScore(string a)
    {
      int score = 0;
     
      for(int i=0;i<a.length();i++)
      {
      	if(a[i]>=65&&a[i]<=90)
        score +=( a[i]-'A'+1 );
      }
      return score;
    }
    
    bool isTriangular(int a)
    {
      double m = (sqrt(8*(double)a+1) - 1) / 2;
      if(floor(m)==m) return true;
      return false;
    }
    
    int main()
    {	
      int ans = 0;
      string word;
      ifstream fin("words.txt");
      if (fin.is_open())
      {
        while (getline(fin,word,','))
        {
          if(isTriangular( wordScore(word) ) )
    	  {
            ans++;
          }
        }
        fin.close();
      }
      cout << ans << endl;
      return 0;
    }

[words.txt]: https://projecteuler.net/project/resources/p042_words.txt
[20161030151934799]: /images/20220715/cad68d86d65c4c488f54a661def0a827.png