Add more Leetcode solutions.

Add more comments and refactoring.

README.md

@@ -4,15 +4,15 @@ Something I have learned...
 ## [Algorithm](./algorithm/)
 | Title | Solution |
 | ----- | -------- |
-| Array  | <ol><li>[20.py](./algorithm/Array/20.py) Valid Parentheses _(elegant coding)_</li><li>[38.py](./algorithm/Array/38.py) Count and Say _(count consecutive elements)_</li><li>[42.py](./algorithm/Array/42.py) Trapping Rain Water _(two pointers)_</li><li>[45.py](./algorithm/Array/45.py) Jump Game II _(till and farest reach)_</li><li>[155.py](./algorithm/Array/155.py) Min Stack</li><li>[209.py](./algorithm/Array/209.py) Summary Ranges _(left pointer and accumulate)_</li><li>[217.py](./algorithm/Array/217.py) Contains Duplicate _(set)_</li><li>[219.py](./algorithm/Array/219.py) Contains Duplicate II _(just cares last)_</li><li>[228.py](./algorithm/Array/228.py) Summary Ranges _(count consecutive elements)_</li><li>[238.py](./algorithm/Array/238.py) Product of Array Except Self _(left2right, right2left)_</li><li>[242.py](./algorithm/Array/242.py) Valid Anagram _(counter equality)_</li><li>[348.py](./algorithm/Array/348.py) Design Tic-Tac-Toe _(diagonal math, sum, loop else)_</li><li>[349.py](./algorithm/Array/349.py) Intersection of Two Arrays _(set & set)_</li><li>[350.py](./algorithm/Array/350.py) Intersection of Two Arrays II _(counter & counter)_</li><li>[388.py](./algorithm/Array/388.py) Longest Absolute File Path _(split, lstrip, memorization)_</li><li>[838.py](./algorithm/Array/838.py) Push Dominoes _(force propagate/reset)_</li><li>[859.py](./algorithm/Array/859.py) Buddy Strings _(enumerate cases)_</li><li>[1002.py](./algorithm/Array/1002.py) Find Common Characters _(counter & counter)_</li><li>[1169.py](./algorithm/Array/1169.py) Invalid Transactions _(permutations)_</li><li>[1170.py](./algorithm/Array/1170.py) Compare Strings by Frequency of the Smallest Character _(minmal counting)_</li><li>[1172.py](./algorithm/Array/1172.py) Dinner Plate Stacks _(heap, responsibilities)_</li><li>[1224.py](./algorithm/Array/1224.py) Maximum Equal Frequency</li><li>[1239.py](./algorithm/Array/1239.py) Maximum Length of a Concatenated String with Unique Characters _(set operation)_</li><li>[1247.py](./algorithm/Array/1247.py) Minimum Swaps to Make Strings Equal _(meaning of swap)_</li><li>[1260.py](./algorithm/Array/1260.py) Shift 2D Grid _(serialize and shift)_</li><li>[5181.py](./algorithm/Array/5181.py) Distance Between Bus Stops</li><li>[5222.py](./algorithm/Array/5222.py) Split a String in Balanced Strings</li></ol> |
+| Array  | <ol><li>[20.py](./algorithm/Array/20.py) Valid Parentheses _(elegant coding)_</li><li>[38.py](./algorithm/Array/38.py) Count and Say _(count consecutive elements)_</li><li>[42.py](./algorithm/Array/42.py) Trapping Rain Water _(two pointers)_</li><li>[45.py](./algorithm/Array/45.py) Jump Game II _(till and farest reach)_</li><li>[155.py](./algorithm/Array/155.py) Min Stack</li><li>[209.py](./algorithm/Array/209.py) Summary Ranges _(left pointer and accumulate)_</li><li>[217.py](./algorithm/Array/217.py) Contains Duplicate _(set)_</li><li>[219.py](./algorithm/Array/219.py) Contains Duplicate II _(just cares last)_</li><li>[228.py](./algorithm/Array/228.py) Summary Ranges _(count consecutive elements)_</li><li>[238.py](./algorithm/Array/238.py) Product of Array Except Self _(left2right, right2left)_</li><li>[242.py](./algorithm/Array/242.py) Valid Anagram _(counter equality)_</li><li>[348.py](./algorithm/Array/348.py) Design Tic-Tac-Toe _(diagonal math, sum, loop else)_</li><li>[349.py](./algorithm/Array/349.py) Intersection of Two Arrays _(set & set)_</li><li>[350.py](./algorithm/Array/350.py) Intersection of Two Arrays II _(counter & counter)_</li><li>[388.py](./algorithm/Array/388.py) Longest Absolute File Path _(split, lstrip, memorization)_</li><li>[838.py](./algorithm/Array/838.py) Push Dominoes _(force propagate/reset)_</li><li>[859.py](./algorithm/Array/859.py) Buddy Strings _(enumerate cases)_</li><li>[1002.py](./algorithm/Array/1002.py) Find Common Characters _(counter & counter)_</li><li>[1122.py](./algorithm/Array/1122.py) Relative Sort Array _(counter, sort)_</li><li>[1169.py](./algorithm/Array/1169.py) Invalid Transactions _(permutations)_</li><li>[1170.py](./algorithm/Array/1170.py) Compare Strings by Frequency of the Smallest Character _(minmal counting)_</li><li>[1172.py](./algorithm/Array/1172.py) Dinner Plate Stacks _(heap, responsibilities)_</li><li>[1224.py](./algorithm/Array/1224.py) Maximum Equal Frequency</li><li>[1239.py](./algorithm/Array/1239.py) Maximum Length of a Concatenated String with Unique Characters _(set operation)_</li><li>[1247.py](./algorithm/Array/1247.py) Minimum Swaps to Make Strings Equal _(meaning of swap)_</li><li>[1260.py](./algorithm/Array/1260.py) Shift 2D Grid _(serialize and shift)_</li><li>[5181.py](./algorithm/Array/5181.py) Distance Between Bus Stops</li><li>[5222.py](./algorithm/Array/5222.py) Split a String in Balanced Strings</li></ol> |
 | Sort  | <ol><li>[Sorting.py](./algorithm/Sort/Sorting.py)</li><li>[15.py](./algorithm/Sort/15.py) 3Sum _(two pointers)_</li><li>[41.py](./algorithm/Sort/41.py) First Missing Positive</li><li>[49.py](./algorithm/Sort/49.py) Group Anagrams</li><li>[56.py](./algorithm/Sort/56.py) Merge Intervals _(lambda sort key)_</li><li>[75.py](./algorithm/Sort/75.py) Sort Colors</li><li>[220.py](./algorithm/Sort/220.py) Contains Duplicate III</li><li>[253.py](./algorithm/Sort/253.py) Meeting Rooms II</li><li>[295.py](./algorithm/Sort/295.py) Find Median from Data Stream</li><li>[539.py](./algorithm/Sort/539.py) Minimum Time Difference</li><li>[953.py](./algorithm/Sort/953.py) Verifying an Alien Dictionary</li><li>[1051.py](./algorithm/Sort/1051.py) Height Checker</li></ol> |
 | Tree  | <ol><li>[Traversal.py](./algorithm/Tree/Traversal.py) / [BinarySearchTree.py](./algorithm/Tree/BinarySearchTree.py) / [BinaryTreeProperty.py](./algorithm/Tree/BinaryTreeProperty.py)</li><li>[98.py](./algorithm/Tree/98.py) Validate Binary Search Tree _(DFS min,max propagation)_</li><li>[102.py](./algorithm/Tree/102.py) Binary Tree Level Order Traversal _(BFS level propagation)_</li><li>[104.py](./algorithm/Tree/104.py) Maximum Depth of Binary Tree _(BFS level propagation)_</li><li>[105.py](./algorithm/Tree/105.py) Construct Binary Tree from Preorder and Inorder Traversal _(DFS .index and slice)_</li><li>[108.py](./algorithm/Tree/108.py) Convert Sorted Array to Binary Search Tree _(DFS mid and slice)_</li><li>[226.py](./algorithm/Tree/226.py) Invert Binary Tree _(DFS/BFS traversal)_</li><li>[250.py](./algorithm/Tree/250.py) Count Univalue Subtrees _(BFS&DFS check each subtrees)_</li><li>[333.py](./algorithm/Tree/333.py) Largest BST Subtree _(BFS&DFS check each subtrees, size in DFS/root in BFS)_</li><li>[863.py](./algorithm/Tree/863.py) All Nodes Distance K in Binary Tree _(DFS annotate parent, BFS condition traversal)_</li></ol> |
 | Graph | <ol><li>[Graph.py](./algorithm/Graph/Graph.py)</li><li>[200.py](./algorithm/Graph/200.py) Number of Islands</li><li>[1222.py](./algorithm/Graph/1222.py) Queens That Can Attack the King</li></ol> |
 | LinkedList | <ol><li>[19.py](./algorithm/LinkedList/19.py) Remove Nth Node From End of List</li><li>[141.py](./algorithm/LinkedList/141.py) Linked List Cycle _(slow/fast pointers)_</li><li>[206.py](./algorithm/LinkedList/206.py) Reverse Linked List _(prev/curr pointers)_</li><li>[160.py](./algorithm/LinkedList/160.py) Intersection of Two Linked Lists</li><li>[1171.py](./algorithm/LinkedList/1171.py) Remove Zero Sum Consecutive Nodes from Linked List</li></ol> |
 | Dynamic Programming | <ol><li>[55.py](./algorithm/DP/55.py) Jump Game</li><li>[62.py](./algorithm/DP/62.py) Unique Paths</li><li>[70.py](./algorithm/DP/70.py) Climbing Stairs</li><li>[72.py](./algorithm/DP/72.py) Edit Distance</li><li>[1223.py](./algorithm/DP/1223.py) Dice Roll Simulation</li></ol> |
-| Sub Array<br>Sub String | <ol><li>[53.py](./algorithm/Sub/53.py) Maximum Subarray _(add or new sum)_</li><li>[121.py](./algorithm/Sub/121.py) Best Time to Buy and Sell Stock _(just cares last)_</li><li>[152.py](./algorithm/Sub/152.py) Maximum Product Subarray _(min * negative)_</li><li>[386.py](./algorithm/Sub/386.py) Longest Substring with At Most K Distinct Characters _(just cares last, idx-left+1)_</li><li>[1233.py](./algorithm/Sub/1233.py) Remove Sub-Folders from the Filesystem _(rfind, set lookup)_</li><li>[1248.py](./algorithm/Sub/1248.py) Count Number of Nice Subarrays _(idx-left+1)_</li></ol> |
+| Sub Array<br>Sub String | <ol><li>[53.py](./algorithm/Sub/53.py) Maximum Subarray _(add or new subsum)_</li><li>[121.py](./algorithm/Sub/121.py) Best Time to Buy and Sell Stock _(just cares last)_</li><li>[152.py](./algorithm/Sub/152.py) Maximum Product Subarray _(min * negative)_</li><li>[386.py](./algorithm/Sub/386.py) Longest Substring with At Most K Distinct Characters _(just cares last, idx-left+1)_</li><li>[1233.py](./algorithm/Sub/1233.py) Remove Sub-Folders from the Filesystem _(rfind, set lookup)_</li><li>[1248.py](./algorithm/Sub/1248.py) Count Number of Nice Subarrays _(atMost(k)-atMost(k - 1))_</li></ol> |
 | Binary Search | <ol><li>[BinarySearchVariants.py](./algorithm/BinarySearch/BinarySearchVariants.py)</li><li>[33.py](./algorithm/BinarySearch/33.py) Search in Rotated Sorted Array _(check sorted part)_</li><li>[1237.py](./algorithm/BinarySearch/1237.py) Find Positive Integer Solution for a Given Equation  _(search in constraint range)_</li></ol> |
-| Math | <ol><li>[The Aggregate Magic Algorithms](http://aggregate.org/MAGIC/)</li><li>[1.py](./algorithm/Math/1.py) Two Sum</li><li>[7.py](./algorithm/Math/7.py) Reverse Integer</li><li>[172.py](./algorithm/Math/172.py) Factorial Trailing Zeroes</li><li>[224.py](./algorithm/Math/224.py) Basic Calculator</li><li>[1071.py](./algorithm/Math/1071.py) Greatest Common Divisor of Strings _(GCD(b, a%b))_</li><li>[1232.py](./algorithm/Math/1232.py) Check If It Is a Straight Line _(dx1*dy2=dy1*dx2)_</li><li>[1238.py](./algorithm/Math/1238.py) Circular Permutation in Binary Representation _(gray code x  ^ x>>1)_</li><li>[1262.py](./algorithm/Math/1262.py) Greatest Sum Divisible by Three _(modulo removal)_</li><li>[5183.py](./algorithm/Math/5183.py) Day of the Week</li></ol> |
+| Math | <ol><li>[The Aggregate Magic Algorithms](http://aggregate.org/MAGIC/)</li><li>[1.py](./algorithm/Math/1.py) Two Sum</li><li>[7.py](./algorithm/Math/7.py) Reverse Integer  _(while != 0)_</li><li>[172.py](./algorithm/Math/172.py) Factorial Trailing Zeroes _(while != 0)_</li><li>[224.py](./algorithm/Math/224.py) Basic Calculator</li><li>[1071.py](./algorithm/Math/1071.py) Greatest Common Divisor of Strings _(GCD(b, a%b))_</li><li>[1232.py](./algorithm/Math/1232.py) Check If It Is a Straight Line _(dx1*dy2=dy1*dx2)_</li><li>[1238.py](./algorithm/Math/1238.py) Circular Permutation in Binary Representation _(gray code x  ^ x>>1)_</li><li>[1262.py](./algorithm/Math/1262.py) Greatest Sum Divisible by Three _(modulo removal)_</li><li>[5183.py](./algorithm/Math/5183.py) Day of the Week</li></ol> |
 
 ## [Bash](./bash/)
 * Bash Reference Manual: [link](https://www.gnu.org/software/bash/manual/bash.html)

algorithm/Array/1122.py

@@ -0,0 +1,48 @@
+'''
+1122. Relative Sort Array
+https://leetcode.com/problems/relative-sort-array/
+
+Given two arrays arr1 and arr2, 
+the elements of arr2 are distinct, 
+and all elements in arr2 are also in arr1.
+
+Sort the elements of arr1 such that 
+the relative ordering of items in arr1 are the same as in arr2.
+Elements that don't appear in arr2 should be 
+placed at the end of arr1 in ascending order.
+
+Example 1:
+Input: arr1 = [2,3,1,3,2,4,6,7,9,2,19], arr2 = [2,1,4,3,9,6]
+Output: [2,2,2,1,4,3,3,9,6,7,19]
+
+Constraints:
+arr1.length, arr2.length <= 1000
+0 <= arr1[i], arr2[i] <= 1000
+Each arr2[i] is distinct.
+Each arr2[i] is in arr1.
+'''
+from typing import *
+import collections
+
+class Solution:
+    def relativeSortArray(self, arr1: List[int], arr2: List[int]) -> List[int]:
+        ans = []
+        c1 = collections.Counter(arr1)
+        for num in arr2:
+            ans.extend([num] * c1[num])
+            del c1[num]
+        remain = list(c1.keys())
+        for num in sorted(remain):
+            # remain num should appear the same times
+            ans.extend([num] * c1[num])
+        return ans
+
+arr1 = [2,3,1,3,2,4,6,7,9,2,19]
+arr2 = [2,1,4,3,9,6]
+print(Solution().relativeSortArray(arr1, arr2))
+# [2,2,2,1,4,3,3,9,6,7,19]
+
+arr1 = [2,21,43,38,0,42,33,7,24,13,12,27,12,24,5,23,29,48,30,31]
+arr2 = [2,42,38,0,43,21]
+print(Solution().relativeSortArray(arr1, arr2))
+# [2,42,38,0,43,21,5,7,12,12,13,23,24,24,27,29,30,31,33,48]

algorithm/Sub/121.py

@@ -26,15 +26,18 @@
 
 class Solution:
     def maxProfit(self, prices: List[int]) -> int:
+        # check not empty
+        # avoid array index out of range for prices[0]
+        if not prices:
+            return 0
         profit = 0
-        if prices:
-            minPrice = prices[0]
-            for pidx in range(1, len(prices)):
-                # ONLY cares largest peak 
-                # following the smallest valley, 
-                # keep updating valid result
-                minPrice = min(minPrice, prices[pidx])
-                profit = max(profit, prices[pidx]-minPrice)
+        minPrice = prices[0]
+        for pidx in range(1, len(prices)):
+            # ONLY cares largest peak 
+            # following the smallest valley, 
+            # keep updating valid result
+            minPrice = min(minPrice, prices[pidx])
+            profit = max(profit, prices[pidx]-minPrice)
         return profit
 
 print(Solution().maxProfit([7,1,5,3,6,4]))

algorithm/Sub/1233.py

@@ -40,16 +40,17 @@
 class Solution:
     def removeSubfolders(self, folder: List[str]) -> List[str]:
         ans = []
-        set = { f for f in folder }
+        folderSet = set(folder)
         for f in folder:
             path = f
             while path:
                 # Cut down last ..."/xx" to move 
                 # upper level and look for it in set
                 path = path[:path.rfind('/')]
-                if path in set:
+                if path in folderSet:
                     break
             else:
+                # Append if no break
                 ans.append(f)
         return ans
 

algorithm/Sub/152.py

@@ -20,6 +20,10 @@
 
 class Solution:
     def maxSubProduct(self, nums: List[int]) -> int:
+        # check not empty
+        # avoid array index out of range for prices[0]
+        if not nums:
+            return 0
         subMax = subMin = maxSubProd = nums[0]
         #print("maxSubProd:{0}".format(maxSubProd))
         for i in range(1, len(nums)):

algorithm/Sub/53.py

@@ -21,6 +21,8 @@
 class Solution:
 
     def maxSubArray(self, nums: List[int]) -> int:
+        # check not empty
+        # avoid array index out of range for nums[0]
         if not nums:
             return 0
         maxSubSum = nums[0]
@@ -39,4 +41,5 @@ def maxSubArray(self, nums: List[int]) -> int:
             dp[i] = max(dp[i-1]+nums[i], nums[i])
         return max(dp)
 
-print(Solution().maxSubArray([-2,1,-3,4,-1,2,1,-5,4]))
+print(Solution().maxSubArray([-2,1,-3,4,-1,2,1,-5,4]))
+# 6