How to Solve the 132 Pattern in Java
The challenge
Given an array of n
integers nums
, a 132 pattern is a subsequence of three integers nums[i]
, nums[j]
and nums[k]
such that i < j < k
and nums[i] < nums[k] < nums[j]
.
Return true
if there is a 132 pattern in nums
, otherwise, return false
.
**Follow up: **The O(n^2)
is trivial, could you come up with the O(n logn)
or the O(n)
solution?
Example 1:
Input: nums = [1,2,3,4] Output: false Explanation: There is no 132 pattern in the sequence.
Example 2:
Input: nums = [3,1,4,2] Output: true Explanation: There is a 132 pattern in the sequence: [1, 4, 2].
Example 3:
Input: nums = [-1,3,2,0] Output: true Explanation: There are three 132 patterns in the sequence: [-1, 3, 2], [-1, 3, 0] and [-1, 2, 0].
Constraints:
n == nums.length
1 <= n <= 10<sup>4</sup>
-10<sup>9</sup> <= nums[i] <= 10<sup>9</sup>
The solution in Java
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You can also solve this problem by means of using a Stack
.
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