Given an unsorted array return whether an increasing subsequence of length 3 exists or not in the array.
Formally the function should:
Return true if there exists i, j, k
such that arr[i] < arr[j] < arr[k] given 0 ≤ i < j < k ≤ n-1 else return false.
Your algorithm should run in O(n) time complexity and O(1) space complexity.
Examples:
Given [1, 2, 3, 4, 5]
,
return true
.
Given [5, 4, 3, 2, 1]
,
return false
.
class Solution { public: bool increasingTriplet(vector<int>& nums) { int n = nums.size(); int a = INT_MAX; int b = INT_MAX; for (int i = 0; i < n; i++) { if (nums[i] <= a) { a = nums[i]; } else if (nums[i] <= b) { b = nums[i]; } else { return true; } } return false; } };