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Grokking the Coding Interview Patterns in C++

Matchsticks to Square

Explore how to use backtracking to decide if an array of matchsticks can form a perfect square. Learn to apply this combinatorial problem-solving approach for coding interview challenges using efficient algorithms.

We'll cover the following...

Statement

Given an integer array, matchsticks, where matchsticks[i] is the length of the ithith matchstick. Use every single matchstick to create a square. No stick should be broken, although they can be connected, and each matchstick can only be used once.

Return TRUE if we can make this square; otherwise, return FALSE.

Constraints:

  • 1≤1 \leq matchsticks.length ≤15\leq 15

  • 1≤1 \leq matchsticks[i] ≤103\leq 10^3

Examples

Understand the problem

Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

Matchsticks to Square

1.

Can we create a square using the matchsticks below?

matchsticks = [1, 1, 1, 1, 2]

A.

TRUE

B.

FALSE

1 / 2

Figure it out!

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Note: As an additional challenge, we have intentionally hidden the solution to this puzzle.

Sequence - Vertical
Drag and drop the cards to rearrange them in the correct sequence.
1
2
3
4
5
6
7
8

Try it yourself

Implement your solution in the following coding playground.

We have left the solution to this challenge as an exercise for you. An optimal solution to this problem runs in O(n*2n) time and takes O(2n) space. You may try to translate the logic of the solved puzzle into a coded solution.

C++
usercode > main.cpp
bool MatchsticksToSquare(vector<int> matchsticks)

{

    // your code will replace this placeholder return statement

    return false;

}
Matchsticks to Square