chlng28

Author: YuriSpiridonov

Challenges/2021/February-LeetCoding-Challenge.md

@@ -52,6 +52,7 @@ None
 |581.|[Shortest Unsorted Continuous Subarray](https://leetcode.com/problems/shortest-unsorted-continuous-subarray/)|[Python](/Medium/581.ShortestUnsortedContinuousSubarray.py)|Medium|
 |946.|[Validate Stack Sequences](https://leetcode.com/problems/validate-stack-sequences/)|[Python](/Medium/946.ValidateStackSequences.py)|Medium|
 |29.|[Divide Two Integers](https://leetcode.com/problems/divide-two-integers/)|[Python](/Medium/29.DivideTwoIntegers.py)|Medium|
+|895.|[Maximum Frequency Stack](https://leetcode.com/problems/maximum-frequency-stack/)|[Python](/Hard/895.MaximumFrequencyStack.py)|Hard|
 
 ## License
 The code is open-source and licensed under the [MIT License](/LICENSE).

Hard/895.MaximumFrequencyStack.py

@@ -0,0 +1,83 @@
+'''
+    Implement FreqStack, a class which simulates the operation 
+    of a stack-like data structure.
+
+    FreqStack has two functions:
+
+        - push(int x), which pushes an integer x onto the 
+          stack.
+        - pop(), which removes and returns the most frequent 
+          element in the stack.
+            = If there is a tie for most frequent element, 
+              the element closest to the top of the stack is 
+              removed and returned.
+
+    Example:
+    Input: 
+    ["FreqStack","push","push","push","push","push","push","pop","pop","pop","pop"],
+    [[],[5],[7],[5],[7],[4],[5],[],[],[],[]]
+    Output: [null,null,null,null,null,null,null,5,7,5,4]
+    Explanation:
+                 After making six .push operations, the stack 
+                 is [5,7,5,7,4,5] from bottom to top.  Then:
+
+                 pop() -> returns 5, as 5 is the most frequent.
+                 The stack becomes [5,7,5,7,4].
+
+                 pop() -> returns 7, as 5 and 7 is the most 
+                 frequent, but 7 is closest to the top.
+                 The stack becomes [5,7,5,4].
+
+                 pop() -> returns 5.
+                 The stack becomes [5,7,4].
+
+                 pop() -> returns 4.
+                 The stack becomes [5,7].
+
+    Note:
+        - Calls to FreqStack.push(int x) will be such that 
+          0 <= x <= 10^9.
+        - It is guaranteed that FreqStack.pop() won't be 
+          called if the stack has zero elements.
+        - The total number of FreqStack.push calls will not 
+          exceed 10000 in a single test case.
+        - The total number of FreqStack.pop calls will not 
+          exceed 10000 in a single test case.
+        - The total number of FreqStack.push and FreqStack.pop 
+          calls will not exceed 150000 across all test cases.
+'''
+#Dfficulty: Hard
+#37 / 37 test cases passed.
+#Runtime: 9076 ms
+#Memory Usage: 22.3 MB
+
+#Runtime: 9076 ms, faster than 5.05% of Python3 online submissions for Maximum Frequency Stack.
+#Memory Usage: 22.3 MB, less than 64.04% of Python3 online submissions for Maximum Frequency Stack.
+
+class FreqStack:
+
+    def __init__(self):
+        self.stack = []
+        self.count = {}
+
+    def push(self, x: int) -> None:
+        if x not in self.count:
+            self.count[x] = 1
+        else:
+            self.count[x] += 1
+        self.stack.append((x, self.count[x]))
+
+    def pop(self) -> int:
+        max_count = max(self.count, key = self.count.get)
+        length = len(self.stack)
+        while length:
+            length -= 1
+            if self.stack[length][1] == self.count[max_count]:
+                self.count[max_count] -= 1
+                return self.stack.pop(length)[0]        
+
+
+# Your FreqStack object will be instantiated and called as such:
+# obj = FreqStack()
+# obj.push(x)
+# param_2 = obj.pop()

README.md

@@ -1,6 +1,6 @@
 # Python solutions of LeetCode problems.
 ![Language](https://img.shields.io/badge/language-Python-blue.svg) 
-![Problems Solved](https://img.shields.io/badge/problems%20solved-513%2F1609-orange) 
+![Problems Solved](https://img.shields.io/badge/problems%20solved-514%2F1609-orange) 
 [![License](https://img.shields.io/badge/license-MIT-green.svg)](./LICENSE) 
 ![Update](https://img.shields.io/badge/update-Daily-brightgreen.svg) 
 <br><br>
@@ -20,7 +20,7 @@ In this repository provided my Python solutions of LeetCode problems.
 
 2021:
 - [January LeetCoding Challenge](/Challenges/2021/January-LeetCoding-Challenge.md) - 27/31
-- [February LeetCoding Challenge](/Challenges/2021/February-LeetCoding-Challenge.md) - 22/28
+- [February LeetCoding Challenge](/Challenges/2021/February-LeetCoding-Challenge.md) - 23/28
 <br><br>
 ## Solutions
 *P.S. If you like this, please leave me a star.* ★
@@ -328,6 +328,7 @@ In this repository provided my Python solutions of LeetCode problems.
 |881.|[Boats to Save People](https://leetcode.com/problems/boats-to-save-people/)|[Python](/Medium/881.BoatstoSavePeople.py)|Medium|`Two Pointers`|
 |884.|[Uncommon Words from Two Sentences](https://leetcode.com/problems/uncommon-words-from-two-sentences/)|[Python](/Easy/884.UncommonWordsfromTwoSentences.py)|Easy|simple counter|
 |890.|[Find and Replace Pattern](https://leetcode.com/problems/find-and-replace-pattern/)|[Python](/Medium/890.FindandReplacePattern.py)|Medium|`Dictionary`|
+|895.|[Maximum Frequency Stack](https://leetcode.com/problems/maximum-frequency-stack/)|[Python](/Hard/895.MaximumFrequencyStack.py)|Hard||
 |896.|[Monotonic Array](https://leetcode.com/problems/monotonic-array/)|[Python](/Easy/896.MonotonicArray.py)|Easy||
 |897.|[Increasing Order Search Tree](https://leetcode.com/problems/increasing-order-search-tree/)|[Python](/Easy/897.IncreasingOrderSearchTree.py)|Easy|`DFS`, iteratively|
 |900.|[RLE Iterator](https://leetcode.com/problems/rle-iterator/)|[Python](/Medium/900.RLEIterator.py)|Medium||