Improved tasks 27, 28, 36

Author: javadev

LeetCodeNet/G0001_0100/S0027_remove_element/readme.md

@@ -1,22 +1,54 @@
-# 27. Remove Element
+27\. Remove Element
 
-Given an integer array `nums` and an integer `val`, remove all occurrences of `val` in `nums` in-place. The order of the elements may be changed. Then return the number of elements in `nums` which are not equal to `val`.
+Easy
 
-Consider the number of elements in `nums` which are not equal to `val` be `k`, to get accepted, you need to do the following things:
+Given an integer array `nums` and an integer `val`, remove all occurrences of `val` in `nums` [**in-place**](https://en.wikipedia.org/wiki/In-place_algorithm). The relative order of the elements may be changed.
 
-- Change the array `nums` such that the first `k` elements of `nums` contain the elements which are not equal to `val`. The remaining elements of `nums` are not important as well as the size of `nums`.
-- Return `k`.
+Since it is impossible to change the length of the array in some languages, you must instead have the result be placed in the **first part** of the array `nums`. More formally, if there are `k` elements after removing the duplicates, then the first `k` elements of `nums` should hold the final result. It does not matter what you leave beyond the first `k` elements.
 
-## Example 1:
+Return `k` _after placing the final result in the first_ `k` _slots of_ `nums`.
+
+Do **not** allocate extra space for another array. You must do this by **modifying the input array [in-place](https://en.wikipedia.org/wiki/In-place_algorithm)** with O(1) extra memory.
+
+**Custom Judge:**
+
+The judge will test your solution with the following code:
+
+int[] nums = [...]; // Input array 
+
+int val = ...; // Value to remove 
+
+int[] expectedNums = [...]; // The expected answer with correct length.
+                            // It is sorted with no values equaling val. 
+
+int k = removeElement(nums, val); // Calls your implementation 
+
+assert k == expectedNums.length; 
+
+sort(nums, 0, k); // Sort the first k elements of nums 
+
+for (int i = 0; i < actualLength; i++){ 
+
+assert nums[i] == expectedNums[i]; 
+
+}
+
+If all assertions pass, then your solution will be **accepted**.
+
+**Example 1:**
+
+**Input:** nums = [3,2,2,3], val = 3
+
+**Output:** 2, nums = [2,2,\_,\_]
 
-**Input:** nums = `[3,2,2,3]`, val = 3
-**Output:** 2, nums = `[2,2,_,_]`
 **Explanation:** Your function should return k = 2, with the first two elements of nums being 2. It does not matter what you leave beyond the returned k (hence they are underscores).
 
-## Example 2:
+**Example 2:**
+
+**Input:** nums = [0,1,2,2,3,0,4,2], val = 2
+
+**Output:** 5, nums = [0,1,4,0,3,\_,\_,\_]
 
-**Input:** nums = `[0,1,2,2,3,0,4,2]`, val = 2
-**Output:** 5, nums = `[0,1,4,0,3,_,_,_]`
 **Explanation:** Your function should return k = 5, with the first five elements of nums containing 0, 0, 1, 3, and 4. Note that the five elements can be returned in any order. It does not matter what you leave beyond the returned k (hence they are underscores).
 
 **Constraints:**

LeetCodeNet/G0001_0100/S0028_find_the_index_of_the_first_occurrence_in_a_string/readme.md

@@ -1,26 +1,26 @@
-# 28. Find the Index of the First Occurrence in a String
+28\. Find the Index of the First Occurrence in a String
+
+Medium
 
 Given two strings `needle` and `haystack`, return the index of the first occurrence of `needle` in `haystack`, or `-1` if `needle` is not part of `haystack`.
 
-## Example 1:
+**Example 1:**
 
 **Input:** haystack = "sadbutsad", needle = "sad"
+
 **Output:** 0
+
 **Explanation:** "sad" occurs at index 0 and 6. The first occurrence is at index 0, so we return 0.
 
-## Example 2:
+**Example 2:**
 
 **Input:** haystack = "leetcode", needle = "leeto"
-**Output:** -1
-**Explanation:** "leeto" did not occur in "leetcode", so we return -1.
-
-**Clarification:**
 
-What should we return when `needle` is an empty string? This is a great question to ask during an interview.
+**Output:** -1
 
-For the purpose of this problem, we will return 0 when `needle` is an empty string. This is consistent to C's [strstr()](http://www.cplusplus.com/reference/cstring/strstr/) and Java's [indexOf()](https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#indexOf(java.lang.String)).
+**Explanation:** "leeto" did not occur in "leetcode", so we return -1.
 
 **Constraints:**
 
-*   <code>0 <= haystack.length, needle.length <= 5 * 10<sup>4</sup></code>
-*   `haystack` and `needle` consist of only lower-case English characters.
+*   <code>1 <= haystack.length, needle.length <= 10<sup>4</sup></code>
+*   `haystack` and `needle` consist of only lowercase English characters.

LeetCodeNet/G0001_0100/S0036_valid_sudoku/readme.md

@@ -1,10 +1,12 @@
-# 36. Valid Sudoku
+36\. Valid Sudoku
 
-## Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:
+Medium
 
-1.  Each row must contain the digits 1-9 without repetition.
-2.  Each column must contain the digits 1-9 without repetition.
-3.  Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition.
+Determine if a `9 x 9` Sudoku board is valid. Only the filled cells need to be validated **according to the following rules**:
+
+1.  Each row must contain the digits `1-9` without repetition.
+2.  Each column must contain the digits `1-9` without repetition.
+3.  Each of the nine `3 x 3` sub-boxes of the grid must contain the digits `1-9` without repetition.
 
 **Note:**
 
@@ -15,39 +17,53 @@
 
 ![](https://upload.wikimedia.org/wikipedia/commons/thumb/f/ff/Sudoku-by-L2G-20050714.svg/250px-Sudoku-by-L2G-20050714.svg.png)
 
-**Input:**
+**Input:** board = 
+
+[["5","3",".",".","7",".",".",".","."] ,
+
+["6",".",".","1","9","5",".",".","."] ,
+
+[".","9","8",".",".",".",".","6","."] ,
+
+["8",".",".",".","6",".",".",".","3"] ,
+
+["4",".",".","8",".","3",".",".","1"] ,
+
+["7",".",".",".","2",".",".",".","6"] ,
+
+[".","6",".",".",".",".","2","8","."] ,
+
+[".",".",".","4","1","9",".",".","5"] ,
 
-    board =
-    [["5","3",".",".","7",".",".",".","."]
-    ,["6",".",".","1","9","5",".",".","."]
-    ,[".","9","8",".",".",".",".","6","."]
-    ,["8",".",".",".","6",".",".",".","3"]
-    ,["4",".",".","8",".","3",".",".","1"]
-    ,["7",".",".",".","2",".",".",".","6"]
-    ,[".","6",".",".",".",".","2","8","."]
-    ,[".",".",".","4","1","9",".",".","5"]
-    ,[".",".",".",".","8",".",".","7","9"]]
+[".",".",".",".","8",".",".","7","9"]]
 
-**Output:** true 
+**Output:** true
 
 **Example 2:**
 
-**Input:**
+**Input:** board = 
+
+[["8","3",".",".","7",".",".",".","."] ,
+
+["6",".",".","1","9","5",".",".","."] ,
+
+[".","9","8",".",".",".",".","6","."] ,
+
+["8",".",".",".","6",".",".",".","3"] ,
+
+["4",".",".","8",".","3",".",".","1"] ,
+
+["7",".",".",".","2",".",".",".","6"] ,
+
+[".","6",".",".",".",".","2","8","."] ,
+
+[".",".",".","4","1","9",".",".","5"] ,
 
-    board =
-    [["8","3",".",".","7",".",".",".","."]
-    ,["6",".",".","1","9","5",".",".","."]
-    ,[".","9","8",".",".",".",".","6","."]
-    ,["8",".",".",".","6",".",".",".","3"]
-    ,["4",".",".","8",".","3",".",".","1"]
-    ,["7",".",".",".","2",".",".",".","6"]
-    ,[".","6",".",".",".",".","2","8","."]
-    ,[".",".",".","4","1","9",".",".","5"]
-    ,[".",".",".",".","8",".",".","7","9"]]
+[".",".",".",".","8",".",".","7","9"]]
 
 **Output:** false
 
-**Explanation:** Same as Example 1, except with the **5** in the top left corner being modified to **8**. Since there are two 8's in the top left 3x3 sub-box, it is invalid. 
+**Explanation:** Same as Example 1, except with the **5** in the top left corner being modified to **8**. Since there are two 8's in the top left 3x3 sub-box, it is invalid.
 
 **Constraints:**