day 30

Author: sachuverma

Leetcode Daily Challenge/March-2021/30. Russian Doll Envelopes.cpp

@@ -0,0 +1,55 @@
+/*
+Russian Doll Envelopes
+======================
+
+You are given a 2D array of integers envelopes where envelopes[i] = [wi, hi] represents the width and the height of an envelope.
+
+One envelope can fit into another if and only if both the width and height of one envelope is greater than the width and height of the other envelope.
+Return the maximum number of envelopes can you Russian doll (i.e., put one inside the other).
+
+Note: You cannot rotate an envelope.
+
+Example 1:
+Input: envelopes = [[5,4],[6,4],[6,7],[2,3]]
+Output: 3
+Explanation: The maximum number of envelopes you can Russian doll is 3 ([2,3] => [5,4] => [6,7]).
+
+Example 2:
+Input: envelopes = [[1,1],[1,1],[1,1]]
+Output: 1
+
+Constraints:
+1 <= envelopes.length <= 5000
+envelopes[i].length == 2
+1 <= wi, hi <= 104
+*/
+
+class Solution
+{
+  bool static isSmall(vector<int> &a, vector<int> &b)
+  {
+    return a[0] < b[0] && a[1] < b[1];
+  }
+
+public:
+  int maxEnvelopes(vector<vector<int>> &env)
+  {
+    int ans = 1;
+    int n = env.size();
+    vector<int> dp(n, 1);
+    sort(env.begin(), env.end());
+
+    for (int i = 1; i < n; ++i)
+    {
+      int prev = 0;
+      for (int j = 0; j < i; ++j)
+      {
+        if (isSmall(env[j], env[i]))
+          prev = max(prev, dp[j]);
+      }
+      dp[i] = prev + 1;
+      ans = max(ans, dp[i]);
+    }
+    return ans;
+  }
+};

Leetcode Daily Challenge/March-2021/README.md

@@ -31,3 +31,4 @@
 | 27. | [Palindromic Substrings](https://leetcode.com/explore/challenge/card/march-leetcoding-challenge-2021/591/week-4-march-22nd-march-28th/3686/)                               |                         [cpp](./27.%20Palindromic%20Substrings.cpp)                          |
 | 28. | [Reconstruct Original Digits from English](https://leetcode.com/explore/challenge/card/march-leetcoding-challenge-2021/591/week-4-march-22nd-march-28th/3687/)             |             [cpp](./28.%20Reconstruct%20Original%20Digits%20from%20English.cpp)              |
 | 29. | [Flip Binary Tree To Match Preorder Traversal](https://leetcode.com/explore/featured/card/march-leetcoding-challenge-2021/592/week-5-march-29th-march-31st/3689/)          |         [cpp](./29.%20Flip%20Binary%20Tree%20To%20Match%20Preorder%20Traversal.cpp)          |
+| 30. | [Russian Doll Envelopes](https://leetcode.com/explore/challenge/card/march-leetcoding-challenge-2021/592/week-5-march-29th-march-31st/3690/)          |         [cpp](./30.%20Russian%20Doll%20Envelopes.cpp)          |