Author: Vladimir Kheifets vladimir.kheifets@online.de
Copyright © 2025 Vladimir Kheifets All Rights Reserved
An unordered set of dates for one year is given. It is required to obtain an ordered list of months and for each month ordered date intervals. Dates must be specified in two formats:
- full month name and day;
- ISO date format.
"January 8", "May 11", "January 3","January 1", "April 2", "January 4","January 5", "May 11","February 24", "April 1", "February 25", "February 26", "March 12", "January 7", "March 13", "January 3", "March 14", "February 24", "April 3","May 10", "May 12","February 23"
or
"2025-05-10", "2025-03-14","2025-05-11", "2025-01-04", "2025-03-13", "2025-01-08","2025-05-12", "2025-01-03", "2025-04-03","2025-02-24", "2025-01-01", "2025-01-05", "2025-02-23", "2025-02-25", "2025-02-26", "2025-03-12", "2025-04-01", "2025-04-02", "2025-01-07
Intervals:
Days in January
1
3 - 5
7 - 8
Days in February
23 - 26
Days in March
12 - 14
Days in April
1 - 3
Days in May
10 - 12
In order to compare the capabilities of programming languages, the task should be implemented in PHP, Python, C++, Java and ECMAScript.
<?php
/*
Calculating date intervals in PHP
Version: 2.0, 2025-02-22
Author: Vladimir Kheifets vladimir.kheifets@online.de
Copyright © 2025 Vladimir Kheifets All Rights Reserved
*/
function getIntervals($inData){
$months = getMonths();
$groups = [];
foreach((array)$inData as $item){
$pattern1 = "/^([a-zA-Z]+).+(\d+)$/";
$pattern2 = "/^(\d{4})\-(\d{2})\-(\d{2})$/";
if(preg_match($pattern1, $item, $out))
{
$month = array_search($out[1], $months);
$day = intval($out[2]);
}
else if(preg_match($pattern2, $item, $out2))
{
$month = intval($out2[2])-1;
$day = intval($out2[3]);
}
else
return false;
$groups[$month][] = $day;
}
if(empty($groups))
return false;
ksort($groups);
foreach($groups as $preff => $group){
sort($group);
//---------------------------------
$interval = "";
$numberBefor = 0;
foreach($group as $number)
{
if($numberBefor == 0)
$interval = $number;
else
{
if(($number - $numberBefor) > 1)
{
if($interval != $numberBefor)
$interval .= " - $numberBefor";
$intervals[$preff][] = $interval;
$interval = $number;
}
}
$numberBefor = $number;
}
if($interval != $number)
$interval .= " - $number";
$intervals[$preff][] = $interval;
}
return $intervals;
}
//---------------------------------------------------------
function viewIntervals($intervals){
if($intervals)
{
$months = getMonths();
$out = "-----------------------------------<br>";
$out .= "Intervals:<br>";
foreach($intervals as $month => $interval){
$out .= "Days in {$months[$month]}:<br>";
foreach($interval as $numberDays)
{
$out .= "$numberDays<br>";
}
$out .= "<br>";
}
echo $out;
}
}
//---------------------------------------------------------
function getMonths(){
return array_map(fn (int $m): string => (DateTime::createFromFormat('m-d', "$m-1")
-> format('F')), range(1, 12),);
}
//---------------------------------------------------------
$data = ["January 8", "May 11", "January 3","January 1", "April 2", "January 4","January 5", "May 11","February 24", "April 1", "February 25", "February 26", "March 12", "January 7", "March 13", "January 3", "March 14", "February 24", "April 3","May 10", "May 12","February 23"];
$intervals = getIntervals($data);
viewIntervals($intervals);
//-------------------------------------------------------
$data = ["2025-05-10", "2025-03-14","2025-05-11", "2025-01-04", "2025-03-13", "2025-01-08","2025-05-12", "2025-01-03", "2025-04-03","2025-02-24", "2025-01-01", "2025-01-05", "2025-02-23", "2025-02-25", "2025-02-26", "2025-03-12", "2025-04-01", "2025-04-02", "2025-01-07"];
$intervals = getIntervals($data);
viewIntervals($intervals);
/*
-----------------------------------
Intervals:
Days in January:
1
3 - 5
7 - 8
Days in February:
23 - 26
Days in March:
12 - 14
Days in April:
1 - 3
Days in May:
10 - 12
-----------------------------------
Intervals:
Days in January:
01
03 - 05
07 - 08
Days in February:
23 - 26
Days in March:
12 - 14
Days in April:
01 - 03
Days in May:
10 - 12
*/
"""
Calculating date intervals in Python
Version: 2.0, 2025-02-22
Author: Vladimir Kheifets vladimir.kheifets@online.de
Copyright © 2025 Vladimir Kheifets All Rights Reserved
"""
import re
import datetime
import calendar
def getintervals(inData):
groups = {}
patt1 = re.compile(r'^([a-zA-Z]+).+(\d+)$')
patt2 = re.compile(r'^(\d{4})\-(\d{2})\-(\d{2})$')
intervals = {}
for item in inData:
if re.match(patt1,item):
out = patt1.findall(item)
month = list(calendar.month_name).index(out[0][0]);
day = int(out[0][1])
elif re.match(patt2,item):
out = patt2.findall(item)
month = int(out[0][1])
day = int(out[0][2])
else:
return intervals
if month in groups:
groups[month].append(day)
else:
groups[month]=[day]
monthGroups = sorted(list(groups.keys()))
for preff in monthGroups:
group = groups[preff]
group.sort()
numberBefor = 0
for number in group:
val = str(number)
if numberBefor == 0:
interval = val
else:
if number - numberBefor > 1:
valBefor = str(numberBefor)
if interval != valBefor:
interval += " - " + valBefor
if preff in intervals:
intervals[preff].append(interval)
else:
intervals[preff]=[interval]
interval = val
numberBefor = number
if interval != val:
interval += " - " + val;
if preff in intervals:
intervals[preff].append(interval)
else:
intervals[preff] = [interval]
return intervals;
#--------------------------------------
def viewIntervals(intervals):
out = "---------------------\n\n"
out += "intervals:\n\n"
for month in intervals:
out += "Days in " + calendar.month_name[month] + "\n"
for numberDays in intervals[month]:
out += numberDays + "\n"
out += "\n"
print(out)
#--------------------------------------
data = ["January 8", "May 11", "January 3","January 1", "April 2", "January 4","January 5", "May 11","February 24", "April 1", "February 25", "February 26", "March 12", "January 7", "March 13", "January 3", "March 14", "February 24", "April 3","May 10", "May 12","February 23"];
intervals = getintervals(data)
viewIntervals(intervals)
#------------------------------------------------------------
data = ["2025-05-10", "2025-03-14","2025-05-11", "2025-01-04", "2025-03-13", "2025-01-08","2025-05-12", "2025-01-03", "2025-04-03","2025-02-24", "2025-01-01", "2025-01-05", "2025-02-23", "2025-02-25", "2025-02-26", "2025-03-12", "2025-04-01", "2025-04-02", "2025-01-07"];
intervals = getintervals(data)
viewIntervals(intervals)
"""
Output:
---------------------
intervals:
Days in January
1
3 - 5
7 - 8
Days in February
23 - 26
Days in March
12 - 14
Days in April
1 - 3
Days in May
10 - 12
---------------------
intervals:
Days in January
1
3 - 5
7 - 8
Days in February
23 - 26
Days in March
12 - 14
Days in April
1 - 3
Days in May
10 - 12
"""
/*
Calculating date intervals in C++
Version: 2.0, 2025-02-22
Author: Vladimir Kheifets vladimir.kheifets@online.de
Copyright © 2025 Vladimir Kheifets All Rights Reserved
*/
#include <langinfo.h>
#include <locale.h>
#include <iostream>
#include <string>
#include <regex>
#include <map>
using namespace std;
//------------------------------------------------------------
vector<string> getMonths() {
const nl_item nl_months[12] = {MON_1, MON_2, MON_3, MON_4, MON_5, MON_6,
MON_7, MON_8, MON_9, MON_10, MON_11, MON_12};
int i;
vector<string> months;
setlocale(LC_ALL, "");
for (i = 0; i < 12; i++) {
months.push_back(nl_langinfo(nl_months[i]));
}
return months;
}
//------------------------------------------------------------
int getMonthNumber(string month) {
vector<string> months = getMonths();
auto it = find(months.begin(), months.end(), month);
return distance(months.begin(), it);
}
//------------------------------------------------------------
void viewIntervals( map< int, vector<string> > intervals){
vector<string> months;
months = getMonths();
cout << "-----------------------------" << endl << endl;
cout << "Intervals:" << endl << endl;
for (const auto& pair : intervals)
{
int mI = pair.first;
string mN = "Days in " + months[mI] + ":";
cout << mN << endl;
vector interval = pair.second;
for( string numberDay : interval)
{
cout << numberDay << endl;
}
cout << endl;
}
}
//------------------------------------------------------------
map< int, vector <string> > getIntervals(vector<string> inData) {
vector<string> months;
months = getMonths();
map< int, vector<int> > groups;
string interval;
string valBefor;
string val;
vector <int> group;
map< int, vector <string> > intervals = {};
regex rS1("^([a-zA-Z]+).+(\\d+)$");
regex rS2("(\\d{4})\\-(\\d{2})\\-(\\d{2})");
smatch m;
for (string item : inData)
{
int mI;
int d;
if(regex_search(item, m, rS1))
{
mI = getMonthNumber(m[1]);
d = stoi(m[2]);
}
else if(regex_search(item, m, rS2))
{
mI = stoi(m[2]) - 1;
d = stoi(m[3]);
}
else
return intervals;
groups[mI].push_back(d);
}
for (const auto& pair : groups)
{
int month = pair.first;
group = pair.second;
sort(group.begin(), group.end());
int numberBefor = 0;
for (int number : group)
{
val = to_string(number);
if (numberBefor == 0)
interval = val;
else
{
if ((number - numberBefor) > 1)
{
valBefor = to_string(numberBefor);
if (interval != valBefor)
interval += " - " + valBefor;
intervals[month].push_back(interval);
interval = val;
}
}
numberBefor = number;
}
if (interval != val)
interval += " - " + val;
intervals[month].push_back(interval);
}
return intervals;
}
//----------------------------------------------------------------------------
int main()
{
vector<string> data = {"January 8","January 7", "January 3","January 1", "January 4","January 5", "February 23", "February 24", "February 25", "February 26", "March 12", "March 13", "March 14", "April 1", "April 2", "April 3","May 10", "May 11", "May 12"};
map< int, vector <string> > intervals = getIntervals(data);
viewIntervals(intervals);
//------------------------------------------------------
data = {"2025-01-08","2025-01-07", "2025-01-03","2025-01-01", "2025-01-04","2025-01-05", "2025-02-23", "2025-02-24", "2025-02-25", "2025-02-26", "2025-03-12", "2025-03-13", "2025-03-14", "2025-04-01", "2025-04-02", "2025-04-03","2025-05-10", "2025-05-11", "2025-05-12"};
intervals = getIntervals(data);
viewIntervals(intervals);
/*
Intervals:
Days in January
1
3 - 5
7 - 8
Days in February
23 - 26
Days in March
12 - 14
Days in April
1 - 3
Days in May
10 - 12
*/
return 0;
}/*
Calculating date intervals in Java
Version: 2.0, 2025-02-22
Author: Vladimir Kheifets vladimir.kheifets@online.de
Copyright © 2025 Vladimir Kheifets All Rights Reserved
*/
import java.util.*;
import java.util.regex.*;
import java.util.function.Function;
import java.text.SimpleDateFormat;
import java.text.DateFormatSymbols;
public class Main {
public static Map< Integer, Vector<String>> getIntervals(String[] inData)
{
Map< Integer, Vector<Integer> > groups = new HashMap<>();
//List<String> intervals = new ArrayList<String>();
Map< Integer, Vector<String> > intervals = new HashMap<>();
String[] months = new DateFormatSymbols().getMonths();
Pattern p1 = Pattern.compile("^([a-zA-Z]+).+(\\d+)$");
Pattern p2 = Pattern.compile("(\\d{4})\\-(\\d{2})\\-(\\d{2})");
int mI = 0;
int d = 0;
for(String item : inData)
{
Matcher m1 = p1.matcher(item);
boolean b1 = m1.matches();
Matcher m2 = p2.matcher(item);
boolean b2 = m2.matches();
if(b1)
{
mI = Arrays.asList(months).indexOf(m1.group(1));
d = Integer.parseInt(m1.group(2));
}
else if (b2)
{
mI = Integer.parseInt(m2.group(2))-1;
d = Integer.parseInt(m2.group(3));
}
else
return intervals;
if(groups.get(mI) == null)
groups.put(mI, new Vector<Integer>());
groups.get(mI).add(d);
}
groups.entrySet().forEach(entry -> {
int month = entry.getKey();
Vector<Integer> group = new Vector<Integer>();
group = entry.getValue();
Collections.sort(group);
int numberBefor = 0;
String interval = "";
String val = "";
intervals.put(month, new Vector<String>());
for(int number : group)
{
val = Integer.toString(number);
if (numberBefor == 0)
interval = val;
else
{
if (number - numberBefor > 1)
{
String valBefor = Integer.toString(numberBefor);
if (!interval.equals(valBefor))
interval += " - " + valBefor;
//intervals[month].add(interval);
intervals.get(month).add(interval);
interval = val;
}
}
numberBefor = number;
}
if (interval != val)
interval += " - " + val;
intervals.get(month).add(interval);
});
return intervals;
}
//------------------------------------------------------------------------------
public static void viewIntervals(Map< Integer, Vector<String> > intervals){
String[] months = new DateFormatSymbols().getMonths();
System.out.println("------------------------\n");
System.out.println("Intervals:\n");
intervals.entrySet().forEach(entry -> {
int i = entry.getKey();
System.out.println("Days in " + months[i] + ":");
Vector <String> interval = entry.getValue();
for(String numberDay : interval)
System.out.println(numberDay);
System.out.println("");
});
}
//------------------------------------------------------------------------------
public static void main(String[] args) throws Exception{
//------------------------------------------------------------------------------
String[] data1 = {"January 8", "May 11", "January 3","January 1", "April 2", "January 4","January 5", "May 11","February 24", "April 1", "February 25", "February 26", "March 12", "January 7", "March 13", "January 3", "March 14", "February 24", "April 3","May 10", "May 12","February 23"};
Map< Integer, Vector<String>> intervals = getIntervals(data1);
viewIntervals(intervals);
//---------------------------------------------------------------
String[] data2 = {"2025-05-10", "2025-03-14","2025-05-11", "2025-01-04", "2025-03-13", "2025-01-08","2025-05-12", "2025-01-03", "2025-04-03","2025-02-24", "2025-01-01", "2025-01-05", "2025-02-23", "2025-02-25", "2025-02-26", "2025-03-12", "2025-04-01", "2025-04-02", "2025-01-07"};
intervals = getIntervals(data2);
viewIntervals(intervals);
/*
------------------------
Intervals:
Days in January:
1
3 - 5
7 - 8
Days in February:
23 - 26
Days in March:
12 - 14
Days in April:
1 - 3
Days in May:
10 - 12
------------------------
Intervals:
Days in January:
1
3 - 5
7 - 8
Days in February:
23 - 26
Days in March:
12 - 14
Days in April:
1 - 3
Days in May:
10 - 12
*/
}
}/*
Calculating date intervals in ECMAScript
Version: 2.0, 2025-02-22
Author: Vladimir Kheifets vladimir.kheifets@online.de
Copyright © 2025 Vladimir Kheifets All Rights Reserved
*/
function getIntervals(inData){
const pattern1 = /^([a-zA-Z]+).+(\d+)$/;
const pattern2 = /^(\d{4})\-(\d{2})\-(\d{2})$/;
const months = getMonths();
let groups = {};
for(let item of inData)
{
let out1 = pattern1.exec(item);
let out2 = pattern2.exec(item);
let day, month;
if(out1)
{
day = parseInt(out1[2]);
month = months.indexOf(out1[1]);
}
else if(out2)
{
day = parseInt(out2[3]);
month = parseInt(out2[2]) - 1;
}
else
return false;
if(!groups[month])
groups[month]=[];
groups[month].push(day);
}
let intervals = {};
for( let preff in groups)
{
let group = groups[preff];
group.sort();
let numberBefor = 0;
intervals[preff] = [];
for (var number of group)
{
if(numberBefor == 0)
var interval = number;
else
{
if((number - numberBefor) > 1)
{
if(interval != numberBefor)
interval += ` - ${numberBefor}`;
intervals[preff].push(interval);
interval = number;
}
}
numberBefor = number;
}
if(interval != number)
interval += ` - ${number}`;
intervals[preff].push(interval);
}
return intervals;
}
//---------------------------------------------------------
function viewIntervals(intervals){
if(intervals)
{
months = getMonths();
let out = "Intervals:\n\n";
for(var key in intervals )
{
out += `Days in ${months[key]}:\n`;
for(var interval of intervals[key] )
{
out += `${interval}\n`;
}
out += "\n";
}
alert(out);
}
}
//---------------------------------------------------------
function getMonths(){
return months = [...Array(11).keys()].map(key => new Date(0, key).
toLocaleString("en",{ month: 'long' }));
}
//-----------------------------------------------------------
let data = ["January 8", "May 11", "January 3","January 1", "April 2", "January 4","January 5", "May 11","February 24", "April 1", "February 25", "February 26", "March 12", "January 7", "March 13", "January 3", "March 14", "February 24", "April 3","May 10", "May 12","February 23"];
let intervals = getIntervals(data);
viewIntervals(intervals);
//---------------------------------------------------------
data = ["2025-05-10", "2025-03-14","2025-05-11", "2025-01-04", "2025-03-13", "2025-01-08","2025-05-12", "2025-01-03", "2025-04-03","2025-02-24", "2025-01-01", "2025-01-05", "2025-02-23", "2025-02-25", "2025-02-26", "2025-03-12", "2025-04-01", "2025-04-02", "2025-01-07"];
intervals = getIntervals(data);
viewIntervals(intervals);
/*
-----------------------------------
Intervals:
Days in January:
1
3 - 5
7 - 8
Days in February:
23 - 26
Days in March:
12 - 14
Days in April:
1 - 3
Days in May:
10 - 12
-----------------------------------
Intervals:
Days in January:
01
03 - 05
07 - 08
Days in February:
23 - 26
Days in March:
12 - 14
Days in April:
01 - 03
Days in May:
10 - 12
*/