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Valid Arrangement of Pairs

You are given a 0-indexed 2D integer array pairs where pairs[i] = [starti, endi].

You are given a 0-indexed 2D integer array pairs where pairs[i] = [starti, endi]. An arrangement of pairs is valid if for every index i where 1 <= i < pairs.length, we have endi-1 == starti.

Return any valid arrangement of pairs.

Note: The inputs will be generated such that there exists a valid arrangement of pairs.

Valid Arrangement of Pairs diagram

Example 1

Input: pairs = [[5,1],[4,5],[11,9],[9,4]]

Output: [[11,9],[9,4],[4,5],[5,1]]

Explanation: This is a valid arrangement since endi-1 always equals starti. end0 = 9 == 9 = start1 end1 = 4 == 4 = start2 end2 = 5 == 5 = start3

Example 2

Input: pairs = [[1,3],[3,2],[2,1]]

Output: [[1,3],[3,2],[2,1]]

Explanation: This is a valid arrangement since endi-1 always equals starti. end0 = 3 == 3 = start1 end1 = 2 == 2 = start2 The arrangements [[2,1],[1,3],[3,2]] and [[3,2],[2,1],[1,3]] are also valid.

Example 3

Input: pairs = [[1,2],[1,3],[2,1]]

Output: [[1,2],[2,1],[1,3]]

Explanation: This is a valid arrangement since endi-1 always equals starti. end0 = 2 == 2 = start1 end1 = 1 == 1 = start2

Constraints

  • 1 <= pairs.length <= 10^5
  • pairs[i].length == 2
  • 0 <= starti, endi <= 10^9
  • starti != endi
  • No two pairs are exactly the same.
  • There exists a valid arrangement of pairs.

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