@Override
public void reduce(Record key, Iterator<Record> values, TaskContext context) throws IOException {
HashMap<Long, ArrayList<String>> item_date = new HashMap<Long, ArrayList<String>>();
while (values.hasNext()) {
Record val = values.next();
String[] item_info = val.get(0).toString().split(":");
long item_id = Long.parseLong(item_info[0]);
String date_time = item_info[1];
if (!item_date.containsKey(item_id)) {
ArrayList<String> date_list = new ArrayList<String>();
date_list.add(date_time);
item_date.put(item_id, date_list);
} else {
ArrayList<String> date_list = item_date.get(item_id);
date_list.add(date_time);
item_date.put(item_id, date_list);
}
}
// load item_ids into list
Long[] item_id_list = new Long[item_date.size()];
Iterator<Long> item_id_iter = item_date.keySet().iterator();
int count = 0;
while (item_id_iter.hasNext()) {
item_id_list[count] = item_id_iter.next();
count++;
}
// calculate time gap
for (int ii = 0; ii < item_id_list.length; ii++) {
for (int jj = ii + 1; jj < item_id_list.length; jj++) {
long item_id_ii = item_id_list[ii];
long item_id_jj = item_id_list[jj];
ArrayList<String> date_list_ii = item_date.get(item_id_ii);
ArrayList<String> date_list_jj = item_date.get(item_id_jj);
long min_gap = 100000000l;
Iterator<String> date_iter_ii = date_list_ii.iterator();
while (date_iter_ii.hasNext()) {
String date_ii = date_iter_ii.next();
Iterator<String> date_iter_jj = date_list_jj.iterator();
while (date_iter_jj.hasNext()) {
String date_jj = date_iter_jj.next();
long time_gap = get_time_gap(date_ii, date_jj);
if (time_gap < min_gap) {
min_gap = time_gap;
}
}
}
result.set(0, item_id_ii);
result.set(1, item_id_jj);
result.set(2, min_gap);
context.write(result);
}
}
}
@Override
public void setup(TaskContext context) throws IOException {
result = context.createOutputRecord();
}