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.
Note: Your algorithm should run in O(n) time complexity and O(1) space complexity.
Example 1:
Input: [1,2,3,4,5]
Output: true
Example 2:
Input: [5,4,3,2,1]
Output: false
class Solution {
public boolean increasingTriplet(int[] nums) {
// start with two largest values, as soon as we find a number bigger than both,
// while both have been updated, return true.
int small = Integer.MAX_VALUE, big = Integer.MAX_VALUE;
for (int n : nums) {
if (n <= small)
small = n;
// update small if n is smaller than both
else if (n <= big)
big = n;
// update big only if greater than small but smaller than big
else
return true; // return if you find a number bigger than both
}
return false;
}
}