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334.Increasing-Triplet-Subsequence

334. Increasing Triplet Subsequence

题目地址

题目描述

Given an unsorted array return whether an increasing subsequence of length 3 exists or not in the array.
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Formally the function should:
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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.
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Example 1:
Input: [1,2,3,4,5]
Output: true
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Example 2:
Input: [5,4,3,2,1]
Output: false

代码

Approach #1

Time: O(N) && Space: O(1)
class Solution {
public boolean increasingTriplet(int[] nums) {
int small = Integer.MAX_VALUE;
int big = Integer.MAX_VALUE;
for (int n: nums) {
if (n <= small) {
small = n;
} else if (n <= big) {
big = n;
} else {
return true;
}
}
return false;
}
}