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Increasing Triplet Subsequence

Updated: Mar 25, 2021

Given an integer array nums, return true if there exists a triple of indices (i, j, k) such that i < j < k and nums[i] < nums[j] < nums[k]. If no such indices exists, return false.


Example 1:

Input: nums = [1,2,3,4,5]
Output: true
Explanation: Any triplet where i < j < k is valid.

Example 2:

Input: nums = [5,4,3,2,1]
Output: false
Explanation: No triplet exists.

Example 3:

Input: nums = [2,1,5,0,4,6]
Output: true
Explanation: The triplet (3, 4, 5) is valid because nums[3] == 0 < nums[4] == 4 < nums[5] == 6.

Constraints:

  • 1 <= nums.length <= 105

  • -231 <= nums[i] <= 231 - 1

Solution:


class Solution {
    public boolean increasingTriplet(int[] nums) {
        int[] dp = new int[nums.length];
        int max=0;
        
        for(int i=1;i<nums.length;i++)
        {
            for(int j=0;j<i;j++)
            {
                if(nums[i]>nums[j])
                {
                    dp[i]=Math.max(dp[i],dp[j]+1);
                }
            }
            max = Math.max(max,dp[i]);
        }
        return max>=2;
    }
}

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