Computer ScienceSpotting Patterns That Repeat Over and Over
Byte the robot sits cross-legged on a bright classroom rug, holding up a string of colorful beads — red, blue, red, blue — and pointing excitedly at the next empty spot on the string, inviting the learner to guess what bead comes next.
- Identify a repeating pattern in a short sequence of objects or shapes.
- Explain what makes something a pattern by describing the part that repeats.
- Predict what comes next in a simple repeating pattern.
- Distinguish between a sequence that repeats and one that does not.
Key terms
- pattern
- something that happens again and again in the same order
- core
- the smallest part of a pattern that keeps repeating
- predict
- to guess what comes next using the pattern
- sequence
- a row of items lined up one after another
Finding the Core
Every repeating pattern is built from one small piece that keeps coming back, and we call that piece the core. In red, blue, red, blue the core is red, blue, because that pair repeats all the way along. The core is always the smallest part that repeats, so you stop as soon as the pattern starts over. Once you find the core, the whole pattern becomes easy to read, because you just keep saying the core again and again.
Using a Pattern to Predict
The best thing about finding the core is that it lets you predict what comes next, even pieces you cannot see yet. If the core is circle, square, then after a circle it must be the square's turn. Byte's singing trick helps: say the core out loud like a song, and the next note tells you the next piece. Computers use this same idea to guess what comes next in data, which is why spotting patterns is such a useful computing skill.
Not Everything Is a Pattern
It is just as important to know when something is not a repeating pattern. If the pieces do not take turns the same way all the way through, there is no single core, so you cannot guess what comes next. A list like dog, cat, fish, bird never repeats, so it is not a pattern. A list like red, red, blue, yellow, green has a couple of repeats but no core that keeps going. Knowing this keeps you from guessing when there is really nothing to guess from.
Worked examples
Find what comes next in circle, square, circle, square, circle.
- Look for the smallest repeating part: it is circle, square.
- The last shape shown is a circle, so the circle's turn just finished.
- After a circle, the core says it is square's turn next.
Answer: Square comes next.
Find the core of the pattern A, B, A, B, A, B.
- Read along until the pattern starts over: A, B, then A again.
- Because A starts the pattern again after B, the repeating part is A, B.
- Check that A, B repeated three times builds the whole row, which it does.
Answer: The core is A, B.
Activity
Help Byte finish the bead string by placing the missing bead in the right spot.
Practice
Tell what comes next in red, yellow, red, yellow, red, and name the core.
Decide which of these repeats: star, moon, star, moon versus apple, cat, tree, ball.
Common mistakes to avoid
- The next piece is whatever you just saw.The core tells you whose turn is next, which may be different from the piece you just saw.
- The core includes extra repeated pieces.The core is the smallest repeating part, so A, B is the core of A, B, A, B, not A, B, A.
Check your understanding
Byte lines up shapes: circle, square, circle, square, circle, ___. What comes next?
Which of these is a repeating pattern?
A pattern goes A, B, A, B, A, B. What is the core?
Recap
A pattern repeats the same pieces again and again in the same order. The smallest repeating part is called the core, and once you find it you can predict what comes next. Not every list is a pattern; if the pieces do not take turns the same way all the way through, there is no core to follow.
Reflect
Where have you spotted a repeating pattern today, and what was its core?