Longest Increasing Subsequence

Author: sachuverma

Leetcode Daily Challenge/July-2021/09. Longest Increasing Subsequence.cpp

@@ -0,0 +1,54 @@
+/*
+Longest Increasing Subsequence
+==============================
+
+Given an integer array nums, return the length of the longest strictly increasing subsequence.
+
+A subsequence is a sequence that can be derived from an array by deleting some or no elements without changing the order of the remaining elements. For example, [3,6,2,7] is a subsequence of the array [0,3,1,6,2,2,7].
+
+Example 1:
+Input: nums = [10,9,2,5,3,7,101,18]
+Output: 4
+Explanation: The longest increasing subsequence is [2,3,7,101], therefore the length is 4.
+
+Example 2:
+Input: nums = [0,1,0,3,2,3]
+Output: 4
+
+Example 3:
+Input: nums = [7,7,7,7,7,7,7]
+Output: 1
+
+Constraints:
+1 <= nums.length <= 2500
+-104 <= nums[i] <= 104
+
+Follow up: Can you come up with an algorithm that runs in O(n log(n)) time complexity?
+*/
+
+class Solution
+{
+public:
+  int memo[2502][2502];
+
+  int lis(vector<int> &A, int ci, int pi)
+  {
+    if (ci == A.size())
+      return 0;
+    int ans = 0;
+    if (memo[pi + 1][ci + 1] != -1)
+      return memo[pi + 1][ci + 1];
+    if (pi == -1 || A[pi] < A[ci])
+    {
+      ans = max(ans, 1 + lis(A, ci + 1, ci));
+    }
+    ans = max(ans, lis(A, ci + 1, pi));
+    return memo[pi + 1][ci + 1] = ans;
+  }
+
+  int lengthOfLIS(vector<int> &A)
+  {
+    memset(memo, -1, sizeof memo);
+    return lis(A, 0, -1);
+  }
+};

Leetcode Daily Challenge/July-2021/README.md

@@ -9,3 +9,4 @@
 | 6.  | [Reduce Array Size to The Half](https://leetcode.com/explore/challenge/card/july-leetcoding-challenge-2021/608/week-1-july-1st-july-7th/3804/)           |       [cpp](./06.%20Reduce%20Array%20Size%20to%20The%20Half.cpp)       |
 | 7.  | [Kth Smallest Element in a Sorted Matrix](https://leetcode.com/explore/challenge/card/july-leetcoding-challenge-2021/608/week-1-july-1st-july-7th/3805/) | [cpp](./07.%20Kth%20Smallest%20Element%20in%20a%20Sorted%20Matrix.cpp) |
 | 8.  | [Maximum Length of Repeated Subarray](https://leetcode.com/explore/challenge/card/july-leetcoding-challenge-2021/609/week-2-july-8th-july-14th/3807/)    |     [cpp](./08.%20Maximum%20Length%20of%20Repeated%20Subarray.cpp)     |
+| 9.  | [Longest Increasing Subsequence](https://leetcode.com/explore/challenge/card/july-leetcoding-challenge-2021/609/week-2-july-8th-july-14th/3808/)         |         [cpp](./09.%20Longest%20Increasing%20Subsequence.cpp)          |