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IncreasingTripletSubsequence.java
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45 lines (42 loc) · 1.33 KB
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public class IncreasingTripletSubsequence {
public boolean increasingTriplet(int[] nums) {
if (nums.length < 3) {
return false;
}
int prevMin = nums[0];
Integer prevBiggerMin = null;
for (int i = 1; i < nums.length; ++i) {
if (prevBiggerMin != null && nums[i] > prevBiggerMin) {
return true;
}
if (nums[i] > prevMin) {
prevBiggerMin = nums[i];
} else {
prevMin = nums[i];
}
}
return false;
}
//O(n) time and O(1) space
//Can be easily changed to return the triplet.
public boolean increasingTriplet(int[] nums) {
if (nums.length < 3) {
return false;
}
int prevMin = Math.min(nums[0], nums[1]);
int prevLowestPeakId = -1;
if (nums[0] < nums[1]) {
prevLowestPeakId = 1;
}
for (int i = 2; i < nums.length; ++i) {
if (prevLowestPeakId >= 0 && nums[prevLowestPeakId] < nums[i]) {
return true;
}
if (nums[i] > prevMin && ((prevLowestPeakId == -1) || (nums[prevLowestPeakId] > nums[i]))) {
prevLowestPeakId = i;
}
prevMin = Math.min(prevMin, nums[i]);
}
return false;
}
}