Moderate 查单词 @CareerCup

简单题，如果是只查询一次，则用时O(n)

如果要多次查询，则用一个Hashtable存储已查过的词

package Moderate;

import java.util.Hashtable;

import CtCILibrary.AssortedMethods;

/**
 * Design a method to find the frequency of occurrences of any given word in a
 * book.
 * 
 * 译文：
 * 
 * 设计一个函数，找到给定单词在一本书中的出现次数。
 * 
 */
public class S17_9 {

	// 预处理，事先处理好，放在一个Hashtable里
	public static Hashtable<String, Integer> setupDictionary(String[] book) {
		Hashtable<String, Integer> table = new Hashtable<String, Integer>();
		for (String word : book) {
			word = word.toLowerCase();
			if (word.trim() != "") {
				if (!table.containsKey(word)) {
					table.put(word, 0);
				}
				table.put(word, table.get(word) + 1);
			}
		}
		return table;
	}

	public static int getFrequency(Hashtable<String, Integer> table, String word) {
		if (table == null || word == null) {
			return -1;
		}
		word = word.toLowerCase();
		if (table.containsKey(word)) {
			return table.get(word);
		}
		return 0;
	}

	public static void main(String[] args) {
		String[] wordlist = AssortedMethods.getLongTextBlobAsStringList();
		Hashtable<String, Integer> dictionary = setupDictionary(wordlist);

		String[] words = { "the", "Lara", "and", "outcropping", "career", "it" };
		for (String word : words) {
			System.out.println(word + ": " + getFrequency(dictionary, word));
		}
	}
}