LeetCode 3637 | Trionic Array I | Java | Easy | Three-Phase Linear Scan | CodeByTushu
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In today’s video, we solve LeetCode 3637 - Trionic Array I using Array and Two Pointers in Java.
We are given an integer array and need to determine whether it is trionic, meaning it can be partitioned into three consecutive segments: strictly increasing, strictly decreasing, and strictly increasing. This requires identifying two boundary points, a peak and a valley, where the peak index is greater than 0, the valley index is greater than the peak index, and the valley index is less than the last array index.
We employ an optimal three-phase linear traversal: first climbing strictly to peak p, descending strictly to valley q, and finally climbing strictly to the end of the array. The algorithm runs in optimal O(N) time and O(1) auxiliary space, verifying transition bounds at each stage.
🔥 Problem Highlights
✅ Immediate pruning for arrays with length less than 4
✅ Phase 1 verifies strictly increasing ascent to identify the first peak p
✅ Validates that peak p is greater than 0 and less than n - 2
✅ Phase 2 verifies strictly decreasing descent to identify valley q
✅ Validates that valley q is greater than p and less than n - 1
✅ Phase 3 verifies the final strictly increasing ascent to the array end
✅ Time Complexity: O(N) | Space Complexity: O(1) auxiliary memory
⏱️ TIMESTAMPS
00:00 Intro
00:42 Problem Understanding
01:37 Key Observation
02:29 Three-Phase Linear Scan Approach
03:42 Java Code Walkthrough
04:48 Execution and Test Cases
05:59 Time Complexity Analysis
06:37 Space Complexity Analysis
07:04 Outro and Wrap-up
📂 Problem Folder and Detailed Documentation:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/tree/main/solutions/February/3-February/3637-Trionic-Array-I
☕ Java Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/3-February/3637-Trionic-Array-I/Solution.java
🐍 Python Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/3-February/3637-Trionic-Array-I/solution.py
⚡ C++ Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/3-February/3637-Trionic-Array-I/solution.cpp
🌐 JavaScript Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/3-February/3637-Trionic-Array-I/solution.js
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💬 Question of the Day
Why must a trionic array have a minimum length of at least 4 elements?
1️⃣ Because the problem constraints specify that n is at least 4
2️⃣ Because the indices must satisfy the following conditions: peak p is greater than 0, valley q is greater than p, and valley q is less than the last index, requiring at least p = 1, q = 2, and the last index to be at least 3
3️⃣ Because the numbers in the array must all be unique
4️⃣ Because three segments always require at least 5 elements
#LeetCode3637 #LeetCode #TrionicArrayI #Java #JavaDSA #Array #TwoPointers #Simulation #DSA #CodingInterview #ProblemSolving #LeetCodeEasy #DailyLeetCode #JavaProgramming #CodeByTushu
👇 Comment the answer below! 🔥 Close description
In today’s video, we solve LeetCode 3637 - Trionic Array I using Array and Two Pointers in Java.
We are given an integer array and need to determine whether it is trionic, meaning it can be partitioned into three consecutive segments: strictly increasing, strictly decreasing, and strictly increasing. This requires identifying two boundary points, a peak and a valley, where the peak index is greater than 0, the valley index is greater than the peak index, and the valley index is less than the last array index.
We employ an optimal three-phase linear traversal: first climbing strictly to peak p, descending strictly to valley q, and finally climbing strictly to the end of the array. The algorithm runs in optimal O(N) time and O(1) auxiliary space, verifying transition bounds at each stage.
🔥 Problem Highlights
✅ Immediate pruning for arrays with length less than 4
✅ Phase 1 verifies strictly increasing ascent to identify the first peak p
✅ Validates that peak p is greater than 0 and less than n - 2
✅ Phase 2 verifies strictly decreasing descent to identify valley q
✅ Validates that valley q is greater than p and less than n - 1
✅ Phase 3 verifies the final strictly increasing ascent to the array end
✅ Time Complexity: O(N) | Space Complexity: O(1) auxiliary memory
⏱️ TIMESTAMPS
00:00 Intro
00:42 Problem Understanding
01:37 Key Observation
02:29 Three-Phase Linear Scan Approach
03:42 Java Code Walkthrough
04:48 Execution and Test Cases
05:59 Time Complexity Analysis
06:37 Space Complexity Analysis
07:04 Outro and Wrap-up
📂 Problem Folder and Detailed Documentation:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/tree/main/solutions/February/3-February/3637-Trionic-Array-I
☕ Java Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/3-February/3637-Trionic-Array-I/Solution.java
🐍 Python Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/3-February/3637-Trionic-Array-I/solution.py
⚡ C++ Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/3-February/3637-Trionic-Array-I/solution.cpp
🌐 JavaScript Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/3-February/3637-Trionic-Array-I/solution.js
🔗 LeetCode Source Code
📌 Admin type the link
🌐 All LeetCode Solutions
📌 https://codebytushu.com/Leetcode/
📱 Join CodeByTushu on WhatsApp
Get coding updates, LeetCode solutions, daily questions and more.
https://whatsapp.com/channel/0029Vb8k5mCDeON2Xwlkxe40
❤️ Donate
📌 https://codebytushu.com/Leetcode/donate.php
🔥 Perfect For
LeetCode Easy Problems
Java DSA Preparation
Array Traversal and Monotonicity
Two Pointers Technique
State Transition Verification
Time Complexity Optimization
Coding Interview Preparation
Problem Solving
🌐 Follow CodeByTushu
▶️ YouTube: https://www.youtube.com/@codebytushu
📸 Instagram: https://instagram.com/codebytushu/
💼 LinkedIn: https://www.linkedin.com/company/codebytushu/
🌍 Website: https://codebytushu.com
🐙 GitHub: https://github.com/CodeByTushu
❤️ Don’t Forget To
👍 Like | 💬 Comment | 🔔 Subscribe
💬 Question of the Day
Why must a trionic array have a minimum length of at least 4 elements?
1️⃣ Because the problem constraints specify that n is at least 4
2️⃣ Because the indices must satisfy the following conditions: peak p is greater than 0, valley q is greater than p, and valley q is less than the last index, requiring at least p = 1, q = 2, and the last index to be at least 3
3️⃣ Because the numbers in the array must all be unique
4️⃣ Because three segments always require at least 5 elements
#LeetCode3637 #LeetCode #TrionicArrayI #Java #JavaDSA #Array #TwoPointers #Simulation #DSA #CodingInterview #ProblemSolving #LeetCodeEasy #DailyLeetCode #JavaProgramming #CodeByTushu
👇 Comment the answer below! 🔥 Close description