From da488ed2074a50cd77224061a2c4101847094786 Mon Sep 17 00:00:00 2001
From: Div <divcodings@gmail.com>
Date: Mon, 13 Oct 2025 02:17:58 +0530
Subject: [PATCH] Create longest_increasing_subsequence.cpp

// Longest Increasing Subsequence (LeetCode #300)
// Finds the length of the longest strictly increasing subsequence in an array.
// Implemented using O(n log n) approach with binary search (std::lower_bound).
// Beginner-friendly C++ project for Hacktoberfest 2025.
---
 longest_increasing_subsequence.cpp | 34 ++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 longest_increasing_subsequence.cpp

diff --git a/longest_increasing_subsequence.cpp b/longest_increasing_subsequence.cpp
new file mode 100644
index 0000000..da2f7e3
--- /dev/null
+++ b/longest_increasing_subsequence.cpp
@@ -0,0 +1,34 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+class Solution {
+public:
+    int lengthOfLIS(vector<int>& nums) {
+        vector<int> sub; // stores the current increasing subsequence
+        for (int num : nums) {
+            auto it = lower_bound(sub.begin(), sub.end(), num);
+            if (it == sub.end()) {
+                sub.push_back(num);
+            } else {
+                *it = num; // replace to maintain lowest possible value
+            }
+        }
+        return sub.size();
+    }
+};
+
+// Test Example
+int main() {
+    Solution sol;
+    
+    vector<int> nums1 = {10,9,2,5,3,7,101,18};
+    cout << sol.lengthOfLIS(nums1) << endl; // Output: 4
+
+    vector<int> nums2 = {0,1,0,3,2,3};
+    cout << sol.lengthOfLIS(nums2) << endl; // Output: 4
+
+    vector<int> nums3 = {7,7,7,7,7,7,7};
+    cout << sol.lengthOfLIS(nums3) << endl; // Output: 1
+
+    return 0;
+}