Added tasks 892-923

README.md

@@ -415,6 +415,7 @@
 
 | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
 |-|-|-|-|-|-
+| 0912 |[Sort an Array](src/main/kotlin/g0901_1000/s0912_sort_an_array)| Medium | Array, Sorting, Heap_Priority_Queue, Divide_and_Conquer, Merge_Sort, Bucket_Sort, Counting_Sort, Radix_Sort | 606 | 98.48
 
 #### Udemy 2D Arrays/Matrix
 
@@ -1241,6 +1242,7 @@
 
 | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
 |-|-|-|-|-|-
+| 0911 |[Online Election](src/main/kotlin/g0901_1000/s0911_online_election)| Medium | Array, Hash_Table, Binary_Search, Design | 766 | 83.33
 
 ### Dynamic Programming I
 
@@ -1277,6 +1279,7 @@
 | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
 |-|-|-|-|-|-
 | 0053 |[Maximum Subarray](src/main/kotlin/g0001_0100/s0053_maximum_subarray)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Divide_and_Conquer | 662 | 82.48
+| 0918 |[Maximum Sum Circular Subarray](src/main/kotlin/g0901_1000/s0918_maximum_sum_circular_subarray)| Medium | Array, Dynamic_Programming, Divide_and_Conquer, Queue, Monotonic_Queue | 339 | 86.96
 
 #### Day 6
 
@@ -1472,6 +1475,7 @@
 
 | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
 |-|-|-|-|-|-
+| 0896 |[Monotonic Array](src/main/kotlin/g0801_0900/s0896_monotonic_array)| Easy | Array | 576 | 90.91
 | 0028 |[Find the Index of the First Occurrence in a String](src/main/kotlin/g0001_0100/s0028_implement_strstr)| Easy | Top_Interview_Questions, String, Two_Pointers, String_Matching | 257 | 32.35
 
 #### Day 2
@@ -1550,6 +1554,7 @@
 | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
 |-|-|-|-|-|-
 | 0304 |[Range Sum Query 2D - Immutable](src/main/kotlin/g0301_0400/s0304_range_sum_query_2d_immutable)| Medium | Array, Matrix, Design, Prefix_Sum | 1373 | 85.71
+| 0910 |[Smallest Range II](src/main/kotlin/g0901_1000/s0910_smallest_range_ii)| Medium | Array, Math, Sorting, Greedy | 234 | 100.00
 
 #### Day 14
 
@@ -1693,6 +1698,38 @@
 |------|----------------|-------------|-------------|----------|--------
 | 1143 |[Longest Common Subsequence](src/main/kotlin/g1101_1200/s1143_longest_common_subsequence)| Medium | Top_100_Liked_Questions, String, Dynamic_Programming, Algorithm_II_Day_17_Dynamic_Programming, Dynamic_Programming_I_Day_19, Udemy_Dynamic_Programming | 307 | 38.36
 | 0994 |[Rotting Oranges](src/main/kotlin/g0901_1000/s0994_rotting_oranges)| Medium | Array, Breadth_First_Search, Matrix, Algorithm_I_Day_9_Breadth_First_Search_Depth_First_Search, Level_2_Day_10_Graph/BFS/DFS | 308 | 57.93
+| 0923 |[3Sum With Multiplicity](src/main/kotlin/g0901_1000/s0923_3sum_with_multiplicity)| Medium | Array, Hash_Table, Sorting, Two_Pointers, Counting | 190 | 100.00
+| 0922 |[Sort Array By Parity II](src/main/kotlin/g0901_1000/s0922_sort_array_by_parity_ii)| Easy | Array, Sorting, Two_Pointers | 257 | 87.50
+| 0921 |[Minimum Add to Make Parentheses Valid](src/main/kotlin/g0901_1000/s0921_minimum_add_to_make_parentheses_valid)| Medium | String, Greedy, Stack | 131 | 92.59
+| 0920 |[Number of Music Playlists](src/main/kotlin/g0901_1000/s0920_number_of_music_playlists)| Hard | Dynamic_Programming, Math, Combinatorics | 136 | 100.00
+| 0919 |[Complete Binary Tree Inserter](src/main/kotlin/g0901_1000/s0919_complete_binary_tree_inserter)| Medium | Breadth_First_Search, Tree, Binary_Tree, Design | 225 | 100.00
+| 0918 |[Maximum Sum Circular Subarray](src/main/kotlin/g0901_1000/s0918_maximum_sum_circular_subarray)| Medium | Array, Dynamic_Programming, Divide_and_Conquer, Queue, Monotonic_Queue, Dynamic_Programming_I_Day_5 | 339 | 86.96
+| 0917 |[Reverse Only Letters](src/main/kotlin/g0901_1000/s0917_reverse_only_letters)| Easy | String, Two_Pointers | 126 | 100.00
+| 0916 |[Word Subsets](src/main/kotlin/g0901_1000/s0916_word_subsets)| Medium | Array, String, Hash_Table | 397 | 88.89
+| 0915 |[Partition Array into Disjoint Intervals](src/main/kotlin/g0901_1000/s0915_partition_array_into_disjoint_intervals)| Medium | Array | 510 | 76.92
+| 0914 |[X of a Kind in a Deck of Cards](src/main/kotlin/g0901_1000/s0914_x_of_a_kind_in_a_deck_of_cards)| Easy | Array, Hash_Table, Math, Counting, Number_Theory | 238 | 70.00
+| 0913 |[Cat and Mouse](src/main/kotlin/g0901_1000/s0913_cat_and_mouse)| Hard | Dynamic_Programming, Math, Graph, Memoization, Topological_Sort, Game_Theory | 211 | 100.00
+| 0912 |[Sort an Array](src/main/kotlin/g0901_1000/s0912_sort_an_array)| Medium | Array, Sorting, Heap_Priority_Queue, Divide_and_Conquer, Merge_Sort, Bucket_Sort, Counting_Sort, Radix_Sort, Udemy_Sorting_Algorithms | 606 | 98.48
+| 0911 |[Online Election](src/main/kotlin/g0901_1000/s0911_online_election)| Medium | Array, Hash_Table, Binary_Search, Design, Binary_Search_II_Day_20 | 766 | 83.33
+| 0910 |[Smallest Range II](src/main/kotlin/g0901_1000/s0910_smallest_range_ii)| Medium | Array, Math, Sorting, Greedy, Programming_Skills_II_Day_13 | 234 | 100.00
+| 0909 |[Snakes and Ladders](src/main/kotlin/g0901_1000/s0909_snakes_and_ladders)| Medium | Array, Breadth_First_Search, Matrix | 203 | 100.00
+| 0908 |[Smallest Range I](src/main/kotlin/g0901_1000/s0908_smallest_range_i)| Easy | Array, Math | 202 | 87.50
+| 0907 |[Sum of Subarray Minimums](src/main/kotlin/g0901_1000/s0907_sum_of_subarray_minimums)| Medium | Array, Dynamic_Programming, Stack, Monotonic_Stack | 341 | 100.00
+| 0906 |[Super Palindromes](src/main/kotlin/g0901_1000/s0906_super_palindromes)| Hard | Math, Enumeration | 153 | 100.00
+| 0905 |[Sort Array By Parity](src/main/kotlin/g0901_1000/s0905_sort_array_by_parity)| Easy | Array, Sorting, Two_Pointers | 219 | 75.00
+| 0904 |[Fruit Into Baskets](src/main/kotlin/g0901_1000/s0904_fruit_into_baskets)| Medium | Array, Hash_Table, Sliding_Window | 371 | 100.00
+| 0903 |[Valid Permutations for DI Sequence](src/main/kotlin/g0901_1000/s0903_valid_permutations_for_di_sequence)| Hard | Dynamic_Programming | 140 | 100.00
+| 0902 |[Numbers At Most N Given Digit Set](src/main/kotlin/g0901_1000/s0902_numbers_at_most_n_given_digit_set)| Hard | Array, Dynamic_Programming, Math, Binary_Search | 138 | 100.00
+| 0901 |[Online Stock Span](src/main/kotlin/g0901_1000/s0901_online_stock_span)| Medium | Stack, Design, Monotonic_Stack, Data_Stream | 641 | 75.00
+| 0900 |[RLE Iterator](src/main/kotlin/g0801_0900/s0900_rle_iterator)| Medium | Array, Design, Counting, Iterator | 175 | 83.33
+| 0899 |[Orderly Queue](src/main/kotlin/g0801_0900/s0899_orderly_queue)| Hard | String, Math, Sorting | 148 | 100.00
+| 0898 |[Bitwise ORs of Subarrays](src/main/kotlin/g0801_0900/s0898_bitwise_ors_of_subarrays)| Medium | Array, Dynamic_Programming, Bit_Manipulation | 812 | 100.00
+| 0897 |[Increasing Order Search Tree](src/main/kotlin/g0801_0900/s0897_increasing_order_search_tree)| Easy | Depth_First_Search, Tree, Binary_Tree, Stack, Binary_Search_Tree | 128 | 85.71
+| 0896 |[Monotonic Array](src/main/kotlin/g0801_0900/s0896_monotonic_array)| Easy | Array, Programming_Skills_II_Day_1 | 576 | 90.91
+| 0895 |[Maximum Frequency Stack](src/main/kotlin/g0801_0900/s0895_maximum_frequency_stack)| Hard | Hash_Table, Stack, Design, Ordered_Set | 617 | 100.00
+| 0894 |[All Possible Full Binary Trees](src/main/kotlin/g0801_0900/s0894_all_possible_full_binary_trees)| Medium | Dynamic_Programming, Tree, Binary_Tree, Recursion, Memoization | 257 | 100.00
+| 0893 |[Groups of Special-Equivalent Strings](src/main/kotlin/g0801_0900/s0893_groups_of_special_equivalent_strings)| Medium | Array, String, Hash_Table | 141 | 100.00
+| 0892 |[Surface Area of 3D Shapes](src/main/kotlin/g0801_0900/s0892_surface_area_of_3d_shapes)| Easy | Array, Math, Matrix, Geometry | 180 | 100.00
 | 0891 |[Sum of Subsequence Widths](src/main/kotlin/g0801_0900/s0891_sum_of_subsequence_widths)| Hard | Array, Math, Sorting | 481 | 100.00
 | 0890 |[Find and Replace Pattern](src/main/kotlin/g0801_0900/s0890_find_and_replace_pattern)| Medium | Array, String, Hash_Table | 150 | 100.00
 | 0889 |[Construct Binary Tree from Preorder and Postorder Traversal](src/main/kotlin/g0801_0900/s0889_construct_binary_tree_from_preorder_and_postorder_traversal)| Medium | Array, Hash_Table, Tree, Binary_Tree, Divide_and_Conquer | 168 | 100.00

src/main/kotlin/g0801_0900/s0815_bus_routes/readme.md

@@ -41,9 +41,6 @@ Return _the least number of buses you must take to travel from_ `source` _to_ `t
 ```kotlin
 import java.util.LinkedList
 import java.util.Queue
-import kotlin.collections.ArrayList
-import kotlin.collections.HashSet
-import kotlin.collections.MutableSet
 
 class Solution {
     fun numBusesToDestination(routes: Array<IntArray>, source: Int, target: Int): Int {

src/main/kotlin/g0801_0900/s0819_most_common_word/readme.md

@@ -34,16 +34,14 @@ The words in `paragraph` are **case-insensitive** and the answer should be retur
 ## Solution
 
 ```kotlin
-import java.util.Locale
-
 @Suppress("NAME_SHADOWING")
 class Solution {
     fun mostCommonWord(paragraph: String, banned: Array<String>): String {
         var paragraph = paragraph
-        paragraph = paragraph.replace("\\p{Punct}".toRegex(), " ").lowercase(Locale.getDefault())
+        paragraph = paragraph.replace("\\p{Punct}".toRegex(), " ").lowercase()
         val a = paragraph.split(" ".toRegex()).dropLastWhile { it.isEmpty() }.toTypedArray()
         for (i in banned.indices) {
-            banned[i] = banned[i].lowercase(Locale.getDefault())
+            banned[i] = banned[i].lowercase()
         }
         val map: MutableMap<String, Int> = HashMap()
         for (s in a) {

src/main/kotlin/g0801_0900/s0831_masking_personal_information/readme.md

@@ -86,15 +86,13 @@ Thus, the resulting masked number is "\*\*\*-\*\*\*-7890".
 ## Solution
 
 ```kotlin
-import java.util.Locale
-
 class Solution {
     fun maskPII(s: String): String {
         val masked = StringBuilder()
         return if (Character.isAlphabetic(s[0].code)) {
             val locationOfAtSymbol = s.indexOf("@") - 1
             masked.append(s[0]).append("*****").append(s.substring(locationOfAtSymbol))
-            masked.toString().lowercase(Locale.getDefault())
+            masked.toString().lowercase()
         } else {
             val allDigits = StringBuilder()
             var pointer = -1

src/main/kotlin/g0801_0900/s0843_guess_the_word/readme.md

@@ -48,8 +48,6 @@ For each test case, you have exactly `10` guesses to guess the word. At the end
 ## Solution
 
 ```kotlin
-import java.util.Collections
-
 /*
  * // This is the Master's API interface.
  * // You should not implement it, or speculate about its implementation
@@ -65,8 +63,8 @@ class Solution {
     private var next = 0
 
     fun findSecretWord(wordlist: Array<String>, master: Master) {
-        val list = listOf(*wordlist)
-        Collections.shuffle(list)
+        val list = wordlist.copyOf()
+        list.shuffle()
         val test = BooleanArray(wordlist.size)
         while (true) {
             val num = master.guess(list[next])
@@ -77,7 +75,7 @@ class Solution {
         }
     }
 
-    private fun updateList(list: List<String?>, test: BooleanArray, num: Int) {
+    private fun updateList(list: Array<String>, test: BooleanArray, num: Int) {
         val index = next
         for (i in index + 1 until test.size) {
             if (test[i]) {
@@ -92,10 +90,10 @@ class Solution {
         }
     }
 
-    private fun getSame(word1: String?, word2: String?): Int {
+    private fun getSame(word1: String, word2: String): Int {
         var ret = 0
         for (i in 0..5) {
-            if (word1!![i] == word2!![i]) {
+            if (word1[i] == word2[i]) {
                 ret++
             }
         }

src/main/kotlin/g0801_0900/s0855_exam_room/readme.md

@@ -42,8 +42,6 @@ Implement the `ExamRoom` class:
 ## Solution
 
 ```kotlin
-import java.util.Objects
-
 class ExamRoom() {
     private class Node(var `val`: Int, map: MutableMap<Int?, Node>) {
         var pre: Node? = null
@@ -107,7 +105,7 @@ class ExamRoom() {
         }
         return if (right > max) {
             Node(n - 1, map).insert(tail.pre)
-        } else Node(maxAt, map).insert(Objects.requireNonNull(maxAtLeft))
+        } else Node(maxAt, map).insert(maxAtLeft)
     }
 
     fun leave(p: Int) {

src/main/kotlin/g0801_0900/s0857_minimum_cost_to_hire_k_workers/readme.md

@@ -49,10 +49,8 @@ class Solution {
             workers[i] = Worker(wage[i], quality[i])
         }
         workers.sortBy { it!!.ratio() }
-        val maxHeap = PriorityQueue { a: Int?, b: Int? ->
-            Integer.compare(
-                b!!, a!!
-            )
+        val maxHeap = PriorityQueue { a: Int, b: Int ->
+            b.compareTo(a)
         }
         var sumQuality = 0
         var result = Double.MAX_VALUE

src/main/kotlin/g0801_0900/s0890_find_and_replace_pattern/readme.md

@@ -35,13 +35,11 @@ Recall that a permutation of letters is a bijection from letters to letters: eve
 ## Solution
 
 ```kotlin
-import java.util.Collections
-
 class Solution {
     fun findAndReplacePattern(words: Array<String>, pattern: String): List<String> {
         val finalans: MutableList<String> = ArrayList()
         if (pattern.length == 1) {
-            Collections.addAll(finalans, *words)
+            finalans.addAll(words)
             return finalans
         }
         for (word in words) {

src/main/kotlin/g0801_0900/s0892_surface_area_of_3d_shapes/readme.md

@@ -0,0 +1,81 @@
+[![](https://img.shields.io/github/stars/javadev/LeetCode-in-Kotlin?label=Stars&style=flat-square)](https://github.com/javadev/LeetCode-in-Kotlin)
+[![](https://img.shields.io/github/forks/javadev/LeetCode-in-Kotlin?label=Fork%20me%20on%20GitHub%20&style=flat-square)](https://github.com/javadev/LeetCode-in-Kotlin/fork)
+
+## 892\. Surface Area of 3D Shapes
+
+Easy
+
+You are given an `n x n` `grid` where you have placed some `1 x 1 x 1` cubes. Each value `v = grid[i][j]` represents a tower of `v` cubes placed on top of cell `(i, j)`.
+
+After placing these cubes, you have decided to glue any directly adjacent cubes to each other, forming several irregular 3D shapes.
+
+Return _the total surface area of the resulting shapes_.
+
+**Note:** The bottom face of each shape counts toward its surface area.
+
+**Example 1:**
+
+![](https://assets.leetcode.com/uploads/2021/01/08/tmp-grid2.jpg)
+
+**Input:** grid = \[\[1,2],[3,4]]
+
+**Output:** 34
+
+**Example 2:**
+
+![](https://assets.leetcode.com/uploads/2021/01/08/tmp-grid4.jpg)
+
+**Input:** grid = \[\[1,1,1],[1,0,1],[1,1,1]]
+
+**Output:** 32
+
+**Example 3:**
+
+![](https://assets.leetcode.com/uploads/2021/01/08/tmp-grid5.jpg)
+
+**Input:** grid = \[\[2,2,2],[2,1,2],[2,2,2]]
+
+**Output:** 46
+
+**Constraints:**
+
+*   `n == grid.length == grid[i].length`
+*   `1 <= n <= 50`
+*   `0 <= grid[i][j] <= 50`
+
+## Solution
+
+```kotlin
+class Solution {
+    fun surfaceArea(grid: Array<IntArray>): Int {
+        var surfaceArea = 0
+        for (i in grid.indices) {
+            for (j in grid[i].indices) {
+                if (grid[i][j] > 0) {
+                    surfaceArea += 4 * grid[i][j] + 2
+                    surfaceArea -= hiddenSides(i, j, grid)
+                }
+            }
+        }
+        return surfaceArea
+    }
+
+    private fun hiddenSides(i: Int, j: Int, grid: Array<IntArray>): Int {
+        var hidden = 0
+        val tower = grid[i][j]
+        if (j + 1 < grid[i].size && grid[i][j + 1] > 0) {
+            hidden += tower.coerceAtMost(grid[i][j + 1])
+        }
+        if (j - 1 >= 0 && grid[i][j - 1] > 0) {
+            hidden += tower.coerceAtMost(grid[i][j - 1])
+        }
+        if (i + 1 < grid.size && grid[i + 1][j] > 0) {
+            hidden += tower.coerceAtMost(grid[i + 1][j])
+        }
+        if (i - 1 >= 0 && grid[i - 1][j] > 0) {
+            hidden += tower.coerceAtMost(grid[i - 1][j])
+        }
+        return hidden
+    }
+}
+```

src/main/kotlin/g0801_0900/s0893_groups_of_special_equivalent_strings/readme.md

@@ -0,0 +1,80 @@
+[![](https://img.shields.io/github/stars/javadev/LeetCode-in-Kotlin?label=Stars&style=flat-square)](https://github.com/javadev/LeetCode-in-Kotlin)
+[![](https://img.shields.io/github/forks/javadev/LeetCode-in-Kotlin?label=Fork%20me%20on%20GitHub%20&style=flat-square)](https://github.com/javadev/LeetCode-in-Kotlin/fork)
+
+## 893\. Groups of Special-Equivalent Strings
+
+Medium
+
+You are given an array of strings of the same length `words`.
+
+In one **move**, you can swap any two even indexed characters or any two odd indexed characters of a string `words[i]`.
+
+Two strings `words[i]` and `words[j]` are **special-equivalent** if after any number of moves, `words[i] == words[j]`.
+
+*   For example, `words[i] = "zzxy"` and `words[j] = "xyzz"` are **special-equivalent** because we may make the moves `"zzxy" -> "xzzy" -> "xyzz"`.
+
+A **group of special-equivalent strings** from `words` is a non-empty subset of words such that:
+
+*   Every pair of strings in the group are special equivalent, and
+*   The group is the largest size possible (i.e., there is not a string `words[i]` not in the group such that `words[i]` is special-equivalent to every string in the group).
+
+Return _the number of **groups of special-equivalent strings** from_ `words`.
+
+**Example 1:**
+
+**Input:** words = ["abcd","cdab","cbad","xyzz","zzxy","zzyx"]
+
+**Output:** 3
+
+**Explanation:** 
+
+One group is ["abcd", "cdab", "cbad"], since they are all pairwise special equivalent, and none of the other strings is all pairwise special equivalent to these. 
+
+The other two groups are ["xyzz", "zzxy"] and ["zzyx"].
+
+Note that in particular, "zzxy" is not special equivalent to "zzyx".
+
+**Example 2:**
+
+**Input:** words = ["abc","acb","bac","bca","cab","cba"]
+
+**Output:** 3
+
+**Constraints:**
+
+*   `1 <= words.length <= 1000`
+*   `1 <= words[i].length <= 20`
+*   `words[i]` consist of lowercase English letters.
+*   All the strings are of the same length.
+
+## Solution
+
+```kotlin
+class Solution {
+    fun numSpecialEquivGroups(words: Array<String>): Int {
+        val set: HashSet<String> = HashSet()
+        var result = 0
+        for (str in words) {
+            if (set.add(getHashBySwap(str.toCharArray()))) {
+                result++
+            }
+        }
+        return result
+    }
+
+    private fun getHashBySwap(chars: CharArray): String {
+        for (i in chars.indices) {
+            var j = i + 2
+            while (j < chars.size) {
+                if (chars[i] > chars[j]) {
+                    val temp = chars[j]
+                    chars[j] = chars[i]
+                    chars[i] = temp
+                }
+                j += 2
+            }
+        }
+        return String(chars)
+    }
+}
+```