Project Euler 問題42（三角数単語）を解いてみる

"A","ABILITY","ABLE","ABOUT","ABOVE","ABSENCE","ABSOLUTELY", ...

#include <iostream>
#include <vector>
#include <string>
#include <cctype>

using namespace std;

int calc_score(string word)
{
	int index = 0;
	int score = 0;

	while (word[index] != 0) {
		score += (word[index] - 'A' + 1);
		++index;
	}

	return score;
}

#define TRIANGLE_NUMBER_MAX 10000

int main()
{
	string buffer;
	cin >> buffer; // Read all file.

	vector<bool> is_triangle_number(TRIANGLE_NUMBER_MAX, false);
	int i = 1;
	int j = 2;
	is_triangle_number[1] = 1;
	while (1) {
		i += j;
		++j;
		if (i < TRIANGLE_NUMBER_MAX) {
			is_triangle_number[i] = true;
		} else {
			break;
		}
	}

	vector<string> words;
	string word_buffer;
	bool in_word = false;
	for (size_t i = 0; i < buffer.size(); ++i) {
		if (isalpha(buffer[i])) {
			word_buffer += buffer[i];
			in_word = true;
		} else {
			if (in_word) {
				words.push_back(word_buffer);
				word_buffer.clear();
				in_word = false;
			}
		}
	}
	cout << "number of words :" << words.size() << endl;

	int answer = 0;
	for (auto word : words) {
		int score = calc_score(word);
		if (score >= TRIANGLE_NUMBER_MAX) {
			cout << "Program needs more triangle number table!" << endl;
		}
		if (is_triangle_number[score]) {
			++answer;
		}
	}

	cout << "Problem042: " << answer << endl;

	return 0;
}