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| 1 | +✅ LeetCode 594 – Longest Harmonious Subsequence |
| 2 | + |
| 3 | +public class Solution { |
| 4 | + public int findLHS(int[] nums) { |
| 5 | + Map<Integer, Integer> map = new HashMap<>(); |
| 6 | + int maxLen = 0; |
| 7 | + |
| 8 | + for (int num : nums) { |
| 9 | + map.put(num, map.getOrDefault(num, 0) + 1); |
| 10 | + } |
| 11 | + |
| 12 | + for (int key : map.keySet()) { |
| 13 | + if (map.containsKey(key + 1)) { |
| 14 | + maxLen = Math.max(maxLen, map.get(key) + map.get(key + 1)); |
| 15 | + } |
| 16 | + } |
| 17 | + |
| 18 | + return maxLen; |
| 19 | + } |
| 20 | +} |
| 21 | + |
| 22 | +Explanation |
| 23 | + |
| 24 | +Map<Integer, Integer> map = new HashMap<>(); |
| 25 | +🔹 Har number ka count store karne ke liye frequency map bana rahe hain. |
| 26 | + |
| 27 | +for (int num : nums) |
| 28 | + map.put(num, map.getOrDefault(num, 0) + 1); |
| 29 | + |
| 30 | +🔹 Har element ka occurrence count update karte ja rahe hain. |
| 31 | + |
| 32 | +for (int key : map.keySet()) |
| 33 | +🔹 Har unique element par loop kar rahe hain. |
| 34 | + |
| 35 | +if (map.containsKey(key + 1)) |
| 36 | + maxLen = Math.max(maxLen, map.get(key) + map.get(key + 1)); |
| 37 | + |
| 38 | +🔹 Check kar rahe hain kya key ke next element (key + 1) bhi present hai. |
| 39 | +Agar haan, toh key aur key+1 dono milke ek harmonious subsequence banayenge. |
| 40 | +Unka combined count (frequency) hi subsequence length hoga. |
| 41 | + |
| 42 | +return maxLen; |
| 43 | +🔹 Sabse longest valid subsequence ka length return kar diya. |
| 44 | + |
| 45 | +🧪 Example Dry Run |
| 46 | +Input: |
| 47 | +nums = [1,3,2,2,5,2,3,7] |
| 48 | +Frequency Map: |
| 49 | +1→1, 2→3, 3→2, 5→1, 7→1 |
| 50 | + |
| 51 | +Valid Pairs: |
| 52 | + |
| 53 | +1 & 2 → 1 + 3 = 4 |
| 54 | + |
| 55 | +2 & 3 → 3 + 2 = 5 ✅ |
| 56 | + |
| 57 | +3 & 4 ❌ |
| 58 | + |
| 59 | +5 & 6 ❌ |
| 60 | + |
| 61 | +7 & 8 ❌ |
| 62 | + |
| 63 | +Output: 5 |
| 64 | + |
| 65 | +Time & Space Complexity |
| 66 | +Item Complexity |
| 67 | +Time O(N) |
| 68 | +Space O(N) |
| 69 | + |
| 70 | +🔗 Need more help or Java tricks? |
| 71 | +https://www.linkedin.com/in/saurabh884095/ |
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