659 - Split Array into Consecutive Subsequences\.

Medium

You are given an integer array nums that is sorted in non-decreasing order.

Determine if it is possible to split nums into one or more subsequences such that both of the following conditions are true:

• Each subsequence is a consecutive increasing sequence (i.e. each integer is exactly one more than the previous integer).

• All subsequences have a length of 3 or more.

Return true if you can split nums according to the above conditions, or false otherwise.

A subsequence of an array is a new array that is formed from the original array by deleting some (can be none) of the elements without disturbing the relative positions of the remaining elements. (i.e., [1,3,5] is a subsequence of <code><ins>1</ins>,2,<ins>3</ins>,4,<ins>5</ins></code> while [1,3,2] is not).

Example 1:

Input: nums = 1,2,3,3,4,5

Output: true

Explanation: nums can be split into the following subsequences:

**<ins>1</ins>** , **<ins>2</ins>** , **<ins>3</ins>** ,3,4,5 --> 1, 2, 3

[1,2,3, **3** , **4** , **5** ] --> 3, 4, 5

Example 2:

Input: nums = 1,2,3,3,4,4,5,5

Output: true

Explanation: nums can be split into the following subsequences:

**<ins>1</ins>** , **<ins>2</ins>** , **<ins>3</ins>** ,3, **<ins>4</ins>** ,4, **<ins>5</ins>** ,5 --> 1, 2, 3, 4, 5

1,2,3, **<ins>3</ins>** ,4, **<ins>4</ins>** ,5, **<ins>5</ins>** --> 3, 4, 5

Example 3:

Input: nums = 1,2,3,4,4,5

Output: false

Explanation: It is impossible to split nums into consecutive increasing subsequences of length 3 or more.

Constraints:

• <code>1 <= nums.length <= 10⁴</code>

• -1000 <= nums[i] <= 1000

• nums is sorted in non-decreasing order.