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.
Credits:
Special thanks to @DjangoUnchained for adding this problem and creating all test cases.
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java code:
public class Solution {
public boolean increasingTriplet(int[] nums) {
int max = (1<<31)-1;
int mid = (1<<31)-1;
for(int num : nums) {
if(num <= mid)
mid = num;
else if(num <= max)
max = num;
else
return true;
}
return false;
}
}LeetCode:Increasing Triplet Subsequence
原文：http://blog.csdn.net/itismelzp/article/details/51554985