【LeetCode】334.Increasing Triplet Subsequence（Medium）解题报告

【LeetCode】334.Increasing Triplet Subsequence（Medium）解题报告

题目地址：https://leetcode.com/problems/increasing-triplet-subsequence/description/

题目描述：

  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.

Solution:

//time : O(n)
//space : O(1)
class Solution {
public boolean increasingTriplet(int[] nums) {
int min = Integer.MAX_VALUE , secMin = Integer.MAX_VALUE;
for(int num : nums){
if(num <= min) min = num;
else if(num < secMin) secMin = num;
else if(num > secMin) return true;
}
return false;
}
}

Date：2018年2月22日