java实现apriori算法
public class AprioriAlgorithm {private static final int THRESHOLD = 2;/** * * @Title: appriGen * @Description: 产生频繁1项集* @return ArrayList<ArrayList<String>>* @throws */public ArrayList<ArrayList<String>> freq1Gen(ArrayList<ArrayList<String>> list) {Map<String, Integer> candItemMap = new HashMap<String, Integer>();for(int i = 0; i < list.size(); i++) {for(int j = 0; j < list.get(i).size(); j++) {if(null != candItemMap.get(list.get(i).get(j))) {candItemMap.put(list.get(i).get(j), candItemMap.get(list.get(i).get(j)) + 1);} else {candItemMap.put(list.get(i).get(j), 1);}}}Iterator<String> iter = candItemMap.keySet().iterator();ArrayList<ArrayList<String>> dataList = new ArrayList<ArrayList<String>>();while(iter.hasNext()) {String tmp = iter.next();if(candItemMap.get(tmp) >= THRESHOLD) {ArrayList<String> tmpList = new ArrayList<String>();tmpList.add(tmp);dataList.add(tmpList);}}return dataList;}/** * * @Title: candidateGen * @Description: 由频繁k项集产生频繁k+1项集，dataLength代表item个数* @return ArrayList<ArrayList<String>>* @throws */public ArrayList<ArrayList<String>> freqKGen(ArrayList<ArrayList<String>>candiList, int k, ArrayList<ArrayList<String>> originalData) {ArrayList<ArrayList<String>> res = new ArrayList<ArrayList<String>>();for(int i = 0; i < candiList.size() - 1; i++) {for(int j = i + 1; j < candiList.size(); j++) {ArrayList<String> tmp = new ArrayList<String>();if(k == 1) {tmp.add(candiList.get(i).get(0));tmp.add(candiList.get(j).get(0));} else {for(int p = 0; p < k - 1; p++) {if(candiList.get(i).get(p) != candiList.get(j).get(p)) {break;}tmp.add(candiList.get(i).get(p));if(p == k - 2 && candiList.get(i).get(k-1) != candiList.get(j).get(k-1)) { // 表明前k-1项相等tmp.add(candiList.get(i).get(k-1));tmp.add(candiList.get(j).get(k-1));}}}res.add(tmp);}}Iterator<ArrayList<String>> iter = res.iterator();while(iter.hasNext()) {ArrayList<String> tmp = iter.next();if(AprioriUtil.getFreq(originalData, tmp) < THRESHOLD) {iter.remove();}}return res;}public static void main(String[] args) {ArrayList<ArrayList<String>> list = new ArrayList<ArrayList<String>>();ArrayList<String> tmp = new ArrayList<String>();tmp.add("m");tmp.add("s");tmp.add("e");list.add(tmp);ArrayList<String> tmp1 = new ArrayList<String>();tmp1.add("m");tmp1.add("t");tmp1.add("p");list.add(tmp1);ArrayList<String> tmp2 = new ArrayList<String>();tmp2.add("m");tmp2.add("t");tmp2.add("p");tmp2.add("s");list.add(tmp2);ArrayList<String> tmp3 = new ArrayList<String>();tmp3.add("t");tmp3.add("p");list.add(tmp3);AprioriAlgorithm dd = new AprioriAlgorithm();ArrayList<ArrayList<String>> res = dd.freq1Gen(list);ArrayList<ArrayList<String>> res1 = dd.freqKGen(res, 1, list);ArrayList<ArrayList<String>> res2 = dd.freqKGen(res1, 2, list);ArrayList<ArrayList<String>> res3 = dd.freqKGen(res2, 3, list);ArrayList<ArrayList<String>> res4 = dd.freqKGen(res3, 4, list);System.out.println(res1); }}
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