Codelper — Learn to Code, One Day at a Time.

TODAY11.13Fri · 2026

Today's problem

Learn to Code, One Day at a Time.

two pointerscharacter codesP0155

Cutting the shortest piece from a necklace

There is a necklace of n beads strung in a circle. Each bead has one lowercase English letter on it, and the i-th character of the necklace string S is the i-th bead. Because the necklace is round, the 1st bead comes again after the n-th bead. You want to cut out some consecutive beads so that you have every letter of string T, at least as many times as it appears in T. The beads you cut out start at some bead and continue in the direction of increasing numbers (after the n-th comes the 1st), and the same bead cannot be used twice. Cut out as few beads as possible. If there are several ways, choose the one whose starting bead has the smallest number. Print the number of the starting bead and the number of beads cut out on one line, separated by a space. If no cut works, print -1.

Input: The first line has S and the second line has T.
Both consist of lowercase English letters only.
1 ≤ length n of S ≤ 100,000, 1 ≤ length of T ≤ 100,000
Output: The number of the starting bead and the number of beads on one line, separated by a space, or -1

Example 1 · stdin

cabbad
dc

stdout

6 2

Example 2 · stdin

ab
aa

stdout

-1

main.py Programming language Runtime version

Input (stdin)

When you run, these lines are fed to input()/stdin in order (the program doesn't stop to ask).

$ Ready

Open this on a computer to write and run code. On mobile you can read the problem and the solutions.

Learn

From the basics to sorting and recursion, in the same order for every language — plus what only some languages have, like pointers and classes. Switch languages instantly on any lesson.

    
      ABasics4 lessons
      01Printing to the screenYour first line of code: print text and the result of a calculation.
02Variables and valuesGive a value a name so you can reuse and change it.
03Reading inputRead text and numbers from the keyboard (standard input).
04Arithmetic and divisionAdd, subtract and multiply work the same everywhere — division doesn't.

    
    
      BControl flow4 lessons
      05ConditionsDo different things depending on a condition: if · else if · else, plus switch.
06LoopsDo the same thing many times: for and while.
07More loopsTaking values one by one, going backwards, reading up to an end marker, and the run-at-least-once do-while.
08Booleans and the ternary operatorKeeping true/false in a variable, choosing one of two values, and asking "is it one of these?".

    
    
      CData5 lessons
      09StringsLength, uppercase, reverse, and picking one character.
10Lists and arraysMany values in a row: count, first and last, sum, transform all.
11Working with single charactersOne character as a value: its code, letter arithmetic, the i-th character, repeating.
12Building stringsBuild a string from pieces, join with a separator, print values on one line.
13Editing listsContains, remove, reverse, swap, fill with one value, copy.

    
    
      DFunctions2 lessons
      14FunctionsBundle work under a name, take values and return a result — plus recursion.
15More about functionsScope, returning several values, and passing functions as values.

    
    
      EGoing further10 lessons
      16Dictionaries (maps)Find and update values by key: counting words, checking for a key, iterating in key order.
17SortingPut values in order: smallest first, largest first, or by a rule you choose.
182D lists (grids)Grids of rows and columns: reading them, row and column sums, and neighbours inside the bounds.
19Working with stringsSlicing, finding, replacing, trimming, comparing and padding.
20Integers and floating pointWhy 0.1 + 0.2 isn't 0.3, printing a fixed number of decimals, rounding rules and integer overflow.
21RecursionA function that calls itself: base cases, call-stack depth, loops and memoization.
22Common mistakes and error messagesHow to read error messages, and the mistakes every language shares: off-by-one, = vs ==, integer division, null, out-of-range indexes.
23Absolute value, powers, square rootsDropping the sign, multiplying many times, and finding the value whose square is a number.
24Counting, running totals, groupingIn one pass: count what matches, carry the value so far, and collect items by key.
25Lists of records and enumsCollect records in a list, and give names to a small fixed set of values.

    
    
      FAlgorithms8 lessons
      26Simulation and Brute ForceDo exactly what the story says, step by step, and try every candidate without skipping one.
27Stacks and QueuesA stack hands back the newest item first; a queue hands back the oldest first.
28Binary SearchThrow away half of a sorted range at a time to find a value, or the first position that meets a condition.
29Prefix sums and two pointersGet the sum of any range with one subtraction, and find a range by moving two positions forward only.
30GCD, primes and number basesFind the GCD with remainders, sift out primes with a sieve, and write a number in another base.
31The greedy method and priority queuesTake what looks best at each step, and use a queue that hands out the smallest value right away.
32Graphs and depth-first searchWrite down who is connected to whom, then visit everything you can reach.
33Breadth-first search and topological sortSpread out from the nearest places with a queue to get the fewest steps, and line tasks up so prerequisites come first.

    
    
      GLanguage-specific10 lessons
      34PointersC++ · CCarry around where a value lives (its address) and change the caller's variable.
35Dynamic memoryC++ · CBorrow exactly as much memory as you need at run time, and always give it back.
36StructsC# · C++ · CBundle related values into one unit, and know whether that unit is copied or shared.
37Classes and objectsPython · JavaScript · TypeScript · Java · C# · C++Bundle data (fields) and behavior (methods) into one blueprint, then make many objects from it.
38Interfaces and genericsTypeScript · Java · C#An interface promises "these methods exist"; generics let one function work for many types.
39LINQ and streamsJava · C#Chain filtering, mapping, grouping and sorting into one pipeline instead of writing loops.
40Pythonic codePythonComprehensions, slicing with steps, unpacking, enumerate and zip, in, f-strings, and three traps.
41JavaScript equality and truthinessJavaScript · TypeScript== vs ===, falsy values, ?? vs ||, numbers that are all doubles, undefined vs null, and what TypeScript catches.
42C++ references and the STLC++& and const references, vector/map/set/unordered_map, algorithms that take lambdas, and the copy, invalidation and auto-insert traps.
43What makes Craykon differentCraykonKeywords in your own language, a null that stops calculations, a strict ==, and a switch that never falls through.

    

Problems

Every problem has reference solutions in every language it accepts (usually all 8; language-specific topics like pointers or classes take only those languages), machine-checked to produce identical answers.

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