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copied!<p>Store something like following datastructure:- (following is a pseudo code)</p> <pre><code>ValuesSet ={ apple = {"Austrailia","New Zealand"..} sheep = {"Austrailia","New Zealand"..} } for k in ValuesSet for k1 in k.values() for k2 in k.values() if(k1<k2) Set(k1,k2).add(k) </code></pre> <p>time complextiy: O(No of distinct pairs with similar products)</p> <p><strong>Note:</strong> I might be wrong but i donot think u can reduce this time complexity</p> <p>Following is a java implementation for your problem:-</p> <pre><code>public class PairMatching { HashMap Country; ArrayList CountNames; HashMap ProdtoIndex; ArrayList ProdtoCount; ArrayList ProdNames; ArrayList[][] Pairs; int products=0; int countries=0; public void readfile(String filename) { try { BufferedReader br = new BufferedReader(new FileReader(new File(filename))); String line; CountNames = new ArrayList(); Country = new HashMap<String,Integer>(); ProdtoIndex = new HashMap<String,Integer>(); ProdtoCount = new ArrayList<ArrayList>(); ProdNames = new ArrayList(); products = countries = 0; while((line=br.readLine())!=null) { String[] s = line.split(","); s[0] = s[0].trim(); s[1] = s[1].trim(); int k; if(!Country.containsKey(s[0])) { CountNames.add(s[0]); Country.put(s[0],countries); k = countries; countries++; } else { k =(Integer) Country.get(s[0]); } if(!ProdtoIndex.containsKey(s[1])) { ProdNames.add(s[1]); ArrayList n = new ArrayList(); ProdtoIndex.put(s[1],products); n.add(k); ProdtoCount.add(n); products++; } else { int ind =(Integer)ProdtoIndex.get(s[1]); ArrayList c =(ArrayList) ProdtoCount.get(ind); c.add(k); } } System.out.println(CountNames); System.out.println(ProdtoCount); System.out.println(ProdNames); } catch (FileNotFoundException ex) { Logger.getLogger(PairMatching.class.getName()).log(Level.SEVERE, null, ex); } catch (IOException ex) { Logger.getLogger(PairMatching.class.getName()).log(Level.SEVERE, null, ex); } } void FindPairs() { Pairs = new ArrayList[countries][countries]; for(int i=0;i<ProdNames.size();i++) { ArrayList curr = (ArrayList)ProdtoCount.get(i); for(int j=0;j<curr.size();j++) { for(int k=j+1;k<curr.size();k++) { int u =(Integer)curr.get(j); int v = (Integer)curr.get(k); //System.out.println(u+","+v); if(Pairs[u][v]==null) { if(Pairs[v][u]!=null) Pairs[v][u].add(i); else { Pairs[u][v] = new ArrayList(); Pairs[u][v].add(i); } } else Pairs[u][v].add(i); } } } for(int i=0;i<countries;i++) { for(int j=0;j<countries;j++) { if(Pairs[i][j]==null) continue; ArrayList a = Pairs[i][j]; System.out.print("\n{"+CountNames.get(i)+","+CountNames.get(j)+"} : "); for(int k=0;k<a.size();k++) { System.out.print(ProdNames.get((Integer)a.get(k))+" "); } } } } public static void main(String[] args) { PairMatching pm = new PairMatching(); pm.readfile("Input data/BigData.txt"); pm.FindPairs(); } } </code></pre>

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