package?pku;

import?java.io.BufferedReader;
import?java.io.File;
import?java.io.FileNotFoundException;
import?java.io.FileReader;
import?java.io.IOException;
import?java.util.ArrayList;
import?java.util.Arrays;
import?java.util.List;

public?class?Recommendation?{
	
	public?static?final?int?KNEIGHBOUR?=?3;
	public?static?final?int?COLUMNCOUNT?=?8;	//number?of?items
	public?static?final?int?PREFROWCOUNT?=?20;		
	public?static?final?int?TESTROWCOUNT?=?5;
	
	private?String[]?bookName?=?{“數(shù)據(jù)挖掘：概念與技術(shù)““金融工程““投資銀行學(xué)““算法導(dǎo)論““machine?learning““經(jīng)濟(jì)學(xué)原理““金融的邏輯““Thinking?in?Java“};
	
	public?void?generateRecommendations（）?{
		int[][]?preference?=?readFile（PREFROWCOUNT?“preference.data“）;
		int[][]?test?=?readFile（TESTROWCOUNT?“test.data“）;
		double[][]?similarityMatrix?=?produceSimilarityMatrix（preference）;
//		for?（int?i?=?0;?i?//			for?（int?j?=?0;?j?//				System.out.print（similarityMatrix[i][j]+“?“）;
//			}
//			System.out.println（）;
//		}
		List?neighborSerial?=?new?ArrayList（）;
		for?（int?i?=?0;?i?			neighborSerial.clear（）;
			double?max?=?0;
			int?itemSerial?=?0;
			for?（int?j?=?0;?j?				if（test[i][j]?==?0）?{
					double?similaritySum?=?0;
					double?sum?=?0;
					double?score?=?0;
					neighborSerial?=?findKNeighbors（test[i]?j?similarityMatrix）;
					for?（int?m?=?0;?m?						sum?+=?similarityMatrix[j][neighborSerial.get（m）]?*?test[i][neighborSerial.get（m）];
						similaritySum?+=?similarityMatrix[j][neighborSerial.get（m）];
					}
					score?=?sum?/?similaritySum;
					if（score?>?max）?{
						max?=?score;
						itemSerial?=?j;
					}
				}
			}
			System.out.println（“The?book?recommended?for?user?“+i+“?is:?“+bookName[itemSerial]+“?score:?“+max）;
		}
	}
	
	/**
	?*?This?method?is?used?to?find?the?nearest?K?neighbors?to?the?un_scored?item?
	?*?@param?score
	?*?@param?i
	?*?@param?similarityMatrix
	?*?@return
	?*/
	private?List?findKNeighbors（int[]?scoreint?idouble[][]?similarityMatrix）?{	//該方法有三個(gè)參數(shù)，score表示某一用戶對所有項(xiàng)目的評分；i表示某個(gè)項(xiàng)目的序號
		List?neighborSerial?=?new?ArrayList（）;
		double[]?similarity?=?new?double[similarityMatrix.length];
		for?（int?j?=?0;?j?			if（score[j]?!=?0）?{
				similarity[j]?=?similarityMatrix[j][i];
			}?
			else?{
				similarity[j]?=?0;
			}
		}
		double[]?temp?=?new?double[similarity.length];
		for?（int?j?=?0;?j?			temp[j]?=?similarity[j];
		}
		Arrays.sort（temp）;
		for（int?j?=?0;?j?			for?（int?m?=?temp.length?-?1;?m?>=?temp.length?-?KNEIGHBOUR;?m--）?{
				if?（similarity[j]?==?temp[m]?&&?similarity[j]?!=?0.0）
					neighborSerial.add（new?Integer（j））;
			}	
		}
		return?neighborSerial;
	}
	
	/**
	?*?This?method?is?used?to?produce?similarity?matrix?among?items
	?*?@param?

?屬性????????????大小?????日期????時(shí)間???名稱
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?????文件????????232??2010-04-12?15:04??Collaborative?Filtering\.classpath

?????文件????????399??2010-04-12?15:04??Collaborative?Filtering\.project

?????文件???????5854??2010-04-20?11:31??Collaborative?Filtering\bin\pku\Recommendation.class

?????文件????????340??2010-04-12?16:19??Collaborative?Filtering\preference.data

?????文件???????6073??2010-04-20?11:31??Collaborative?Filtering\src\pku\Recommendation.java

?????文件?????????83??2010-04-12?16:23??Collaborative?Filtering\test.data

?????目錄??????????0??2010-04-15?12:32??Collaborative?Filtering\bin\pku

?????目錄??????????0??2010-04-15?12:32??Collaborative?Filtering\src\pku

?????目錄??????????0??2010-04-15?12:32??Collaborative?Filtering\bin

?????目錄??????????0??2010-04-15?12:32??Collaborative?Filtering\src

?????目錄??????????0??2011-10-16?22:57??Collaborative?Filtering

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