You are given a $2$D integer array pairs where each pairs[i] contains two integers [start_i, end_i]. An arrangement of pairs is considered valid if for every index $i$ satisfying $1 \leq i <$ pairs.length, the ending value of the pair at index $i - 1$ equals the starting value of the pair at index $i$ (that is, end$_{i - 1} =$ start$_i$).

Return any valid arrangement of pairs.

Note: If multiple valid arrangements exist, return any of them.

Constraints:

• $1 \leq$ pairs.length $\leq 10^5$

• pairs[i].length $= 2$

• $0 \leq$ start_i, end_i $\leq 10^9$

• start_i $\neq$ end_i

• No two pairs are identical.

• A valid arrangement of pairs is guaranteed to exist.

Now, 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:

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

Implement your solution in the following coding playground.