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g2001_2100.s2097_valid_arrangement_of_pairs.readme.md Maven / Gradle / Ivy

2097\. Valid Arrangement of Pairs

Hard

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`.

**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 <= 105
*   `pairs[i].length == 2`
*   0 <= starti, endi <= 109
*   starti != endi
*   No two pairs are exactly the same.
*   There **exists** a valid arrangement of `pairs`.