// 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.
public class IncreasingTripletSequence {
public boolean increasingTriplet(int[] nums) {
int firstMin = Integer.MAX_VALUE;
int secondMin = Integer.MAX_VALUE;
for(int n : nums) {
if(n <= firstMin) {
firstMin = n;
} else if(n < secondMin) {
secondMin = n;
} else if(n > secondMin) {
return true;
}
}
return false;
}
}
// 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.
public class IncreasingTripletSequence {
public boolean increasingTriplet(int[] nums) {
int firstMin = Integer.MAX_VALUE;
int secondMin = Integer.MAX_VALUE;
for(int n : nums) {
if(n <= firstMin) {
firstMin = n;
} else if(n < secondMin) {
secondMin = n;
} else if(n > secondMin) {
return true;
}
}
return false;
}
}
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