Problem42

原题：

The nth term of the sequence of triangle numbers is given by, t(n) = 1/2*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 = t10. 
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?

 

分析：

根据题意可以得出 2t(n)= n(n+1) => n*n<2t(n)<(n+1)*(n+1)

 

代码入下：

public class Problem42 {//判断是否为triangle数static boolean isTrangle(int number){int n = (int)Math.sqrt(number*2);if(n*(n+1)==2*number)return true;return false;}static final String fileName = "C://Documents and Settings//wangxm//桌面//words.txt";//从文件中读出数据static String[] getStringByTxt(String fileName){String[] nameList = null;try {DataInputStream din = new DataInputStream(new BufferedInputStream(new FileInputStream(new File(fileName))));byte[] b = new byte[din.available()];din.read(b);din.close();String tempStr = new String(b);nameList = tempStr.replaceAll("/"", "").split(",");} catch (Exception e) {e.printStackTrace();}return nameList;}//计算每个字符串的和static int getTheSumByStr(String str){int sum = 0;char[] numCh = str.toCharArray();for(char c:numCh){sum += c-64; }return sum;}public static void main(String[] args) {int count = 0;String[] nameList = getStringByTxt(fileName);for(String str:nameList){if(isTrangle(getTheSumByStr(str)))count++;}System.out.println("count:"+count);}}