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38 changes: 38 additions & 0 deletions
src/main/java/g0001_0100/s0031_next_permutation/readme.md
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| 31\. Next Permutation | ||
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| Medium | ||
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| Implement **next permutation**, which rearranges numbers into the lexicographically next greater permutation of numbers. | ||
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| If such an arrangement is not possible, it must rearrange it as the lowest possible order (i.e., sorted in ascending order). | ||
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| The replacement must be **[in place](http://en.wikipedia.org/wiki/In-place_algorithm)** and use only constant extra memory. | ||
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| **Example 1:** | ||
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| **Input:** nums = \[1,2,3\] | ||
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| **Output:** \[1,3,2\] | ||
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| **Example 2:** | ||
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| **Input:** nums = \[3,2,1\] | ||
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| **Output:** \[1,2,3\] | ||
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| **Example 3:** | ||
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| **Input:** nums = \[1,1,5\] | ||
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| **Output:** \[1,5,1\] | ||
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| **Example 4:** | ||
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| **Input:** nums = \[1\] | ||
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| **Output:** \[1\] | ||
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| **Constraints:** | ||
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| * `1 <= nums.length <= 100` | ||
| * `0 <= nums[i] <= 100` |
32 changes: 32 additions & 0 deletions
src/main/java/g0001_0100/s0032_longest_valid_parentheses/readme.md
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| 32\. Longest Valid Parentheses | ||
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| Hard | ||
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| Given a string containing just the characters `'('` and `')'`, find the length of the longest valid (well-formed) parentheses substring. | ||
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| **Example 1:** | ||
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| **Input:** s = "(()" | ||
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| **Output:** 2 | ||
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| **Explanation:** The longest valid parentheses substring is "()". | ||
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| **Example 2:** | ||
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| **Input:** s = ")()())" | ||
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| **Output:** 4 | ||
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| **Explanation:** The longest valid parentheses substring is "()()". | ||
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| **Example 3:** | ||
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| **Input:** s = "" | ||
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| **Output:** 0 | ||
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| **Constraints:** | ||
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| * `0 <= s.length <= 3 * 104` | ||
| * `s[i]` is `'('`, or `')'`. |
37 changes: 37 additions & 0 deletions
src/main/java/g0001_0100/s0033_search_in_rotated_sorted_array/readme.md
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| 33\. Search in Rotated Sorted Array | ||
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| Medium | ||
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| There is an integer array `nums` sorted in ascending order (with **distinct** values). | ||
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| Prior to being passed to your function, `nums` is **possibly rotated** at an unknown pivot index `k` (`1 <= k < nums.length`) such that the resulting array is `[nums[k], nums[k+1], ..., nums[n-1], nums[0], nums[1], ..., nums[k-1]]` (**0-indexed**). For example, `[0,1,2,4,5,6,7]` might be rotated at pivot index `3` and become `[4,5,6,7,0,1,2]`. | ||
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| Given the array `nums` **after** the possible rotation and an integer `target`, return _the index of_ `target` _if it is in_ `nums`_, or_ `-1` _if it is not in_ `nums`. | ||
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| You must write an algorithm with `O(log n)` runtime complexity. | ||
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| **Example 1:** | ||
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| **Input:** nums = \[4,5,6,7,0,1,2\], target = 0 | ||
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| **Output:** 4 | ||
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| **Example 2:** | ||
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| **Input:** nums = \[4,5,6,7,0,1,2\], target = 3 | ||
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| **Output:** -1 | ||
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| **Example 3:** | ||
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| **Input:** nums = \[1\], target = 0 | ||
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| **Output:** -1 | ||
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| **Constraints:** | ||
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| * `1 <= nums.length <= 5000` | ||
| * `-104 <= nums[i] <= 104` | ||
| * All values of `nums` are **unique**. | ||
| * `nums` is an ascending array that is possibly rotated. | ||
| * `-104 <= target <= 104` |
34 changes: 34 additions & 0 deletions
...01_0100/s0034_find_first_and_last_position_of_element_in_sorted_array/readme.md
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| 34\. Find First and Last Position of Element in Sorted Array | ||
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| Medium | ||
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| Given an array of integers `nums` sorted in non-decreasing order, find the starting and ending position of a given `target` value. | ||
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| If `target` is not found in the array, return `[-1, -1]`. | ||
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| You must write an algorithm with `O(log n)` runtime complexity. | ||
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| **Example 1:** | ||
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| **Input:** nums = \[5,7,7,8,8,10\], target = 8 | ||
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| **Output:** \[3,4\] | ||
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| **Example 2:** | ||
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| **Input:** nums = \[5,7,7,8,8,10\], target = 6 | ||
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| **Output:** \[-1,-1\] | ||
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| **Example 3:** | ||
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| **Input:** nums = \[\], target = 0 | ||
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| **Output:** \[-1,-1\] | ||
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| **Constraints:** | ||
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| * `0 <= nums.length <= 105` | ||
| * `-109 <= nums[i] <= 109` | ||
| * `nums` is a non-decreasing array. | ||
| * `-109 <= target <= 109` |
44 changes: 44 additions & 0 deletions
src/main/java/g0001_0100/s0035_search_insert_position/readme.md
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| 35\. Search Insert Position | ||
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| Easy | ||
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| Given a sorted array of distinct integers and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order. | ||
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| You must write an algorithm with `O(log n)` runtime complexity. | ||
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| **Example 1:** | ||
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| **Input:** nums = \[1,3,5,6\], target = 5 | ||
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| **Output:** 2 | ||
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| **Example 2:** | ||
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| **Input:** nums = \[1,3,5,6\], target = 2 | ||
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| **Output:** 1 | ||
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| **Example 3:** | ||
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| **Input:** nums = \[1,3,5,6\], target = 7 | ||
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| **Output:** 4 | ||
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| **Example 4:** | ||
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| **Input:** nums = \[1,3,5,6\], target = 0 | ||
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| **Output:** 0 | ||
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| **Example 5:** | ||
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| **Input:** nums = \[1\], target = 0 | ||
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| **Output:** 0 | ||
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| **Constraints:** | ||
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| * `1 <= nums.length <= 104` | ||
| * `-104 <= nums[i] <= 104` | ||
| * `nums` contains **distinct** values sorted in **ascending** order. | ||
| * `-104 <= target <= 104` |
58 changes: 58 additions & 0 deletions
src/main/java/g0001_0100/s0036_valid_sudoku/readme.md
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| 36\. Valid Sudoku | ||
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| Medium | ||
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| Determine if a `9 x 9` Sudoku board is valid. Only the filled cells need to be validated **according to the following rules**: | ||
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| 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. | ||
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| **Note:** | ||
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| * A Sudoku board (partially filled) could be valid but is not necessarily solvable. | ||
| * Only the filled cells need to be validated according to the mentioned rules. | ||
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| **Example 1:** | ||
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|  | ||
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| **Input:** | ||
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| 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"]] | ||
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| **Output:** true | ||
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| **Example 2:** | ||
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| **Input:** | ||
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| 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"]] | ||
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| **Output:** false | ||
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| **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. | ||
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| **Constraints:** | ||
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| * `board.length == 9` | ||
| * `board[i].length == 9` | ||
| * `board[i][j]` is a digit `1-9` or `'.'`. |
52 changes: 52 additions & 0 deletions
src/main/java/g0001_0100/s0037_sudoku_solver/readme.md
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| 37\. Sudoku Solver | ||
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| Hard | ||
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| Write a program to solve a Sudoku puzzle by filling the empty cells. | ||
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| A sudoku solution must satisfy **all of the following rules**: | ||
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| 1. Each of the digits `1-9` must occur exactly once in each row. | ||
| 2. Each of the digits `1-9` must occur exactly once in each column. | ||
| 3. Each of the digits `1-9` must occur exactly once in each of the 9 `3x3` sub-boxes of the grid. | ||
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| The `'.'` character indicates empty cells. | ||
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| **Example 1:** | ||
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|  | ||
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| **Input:** | ||
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| 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"]] | ||
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| **Output:** | ||
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| [["5","3","4","6","7","8","9","1","2"], | ||
| ["6","7","2","1","9","5","3","4","8"], | ||
| ["1","9","8","3","4","2","5","6","7"], | ||
| ["8","5","9","7","6","1","4","2","3"], | ||
| ["4","2","6","8","5","3","7","9","1"], | ||
| ["7","1","3","9","2","4","8","5","6"], | ||
| ["9","6","1","5","3","7","2","8","4"], | ||
| ["2","8","7","4","1","9","6","3","5"], | ||
| ["3","4","5","2","8","6","1","7","9"]] | ||
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| **Explanation:** The input board is shown above and the only valid solution is shown below: | ||
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|  | ||
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| **Constraints:** | ||
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| * `board.length == 9` | ||
| * `board[i].length == 9` | ||
| * `board[i][j]` is a digit or `'.'`. | ||
| * It is **guaranteed** that the input board has only one solution. |
41 changes: 41 additions & 0 deletions
src/main/java/g0001_0100/s0038_count_and_say/readme.md
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| 38\. Count and Say | ||
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| Medium | ||
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| The **count-and-say** sequence is a sequence of digit strings defined by the recursive formula: | ||
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| * `countAndSay(1) = "1"` | ||
| * `countAndSay(n)` is the way you would "say" the digit string from `countAndSay(n-1)`, which is then converted into a different digit string. | ||
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| To determine how you "say" a digit string, split it into the **minimal** number of groups so that each group is a contiguous section all of the **same character.** Then for each group, say the number of characters, then say the character. To convert the saying into a digit string, replace the counts with a number and concatenate every saying. | ||
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| For example, the saying and conversion for digit string `"3322251"`: | ||
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|  | ||
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| Given a positive integer `n`, return _the_ `nth` _term of the **count-and-say** sequence_. | ||
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| **Example 1:** | ||
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| **Input:** n = 1 | ||
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| **Output:** "1" | ||
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| **Explanation:** This is the base case. | ||
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| **Example 2:** | ||
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| **Input:** n = 4 | ||
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| **Output:** "1211" | ||
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| **Explanation:** | ||
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| countAndSay(1) = "1" | ||
| countAndSay(2) = say "1" = one 1 = "11" | ||
| countAndSay(3) = say "11" = two 1's = "21" | ||
| countAndSay(4) = say "21" = one 2 + one 1 = "12" + "11" = "1211" | ||
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| **Constraints:** | ||
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| * `1 <= n <= 30` |
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