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.
代码如下：
public class Solution {
public boolean increasingTriplet(int[] nums) {
if(nums.length<3)
return false;
for(int i=nums.length-1;i>=2;i--)
{
int j=i-1;
for( ;j>=1;j--)
{
if(nums[i]>nums[j])
{
int k=j-1;
for(;k>=0;k--)
{
if(nums[j]>nums[k])
return true;
}
}
}
}
return false;
}
}