# leetcode-master

**Repository Path**: pawpaw2022/leetcode-master

## Basic Information

- **Project Name**: leetcode-master
- **Description**: No description available
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2024-05-29
- **Last Updated**: 2024-07-10

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

<!-- @format -->

# leetcode-master

## [6. Zigzag Conversion](https://leetcode.com/problems/zigzag-conversion/description/?envType=study-plan-v2&envId=top-interview-150)

### Explaination

https://www.youtube.com/watch?v=fxhPxvBAvD0

### Solution

```python
class Solution:
    def convert(self, s: str, numRows: int) -> str:
        if numRows == 1 or numRows >= len(s):
            return s

        rows = [[] for _ in range(numRows)]


        idx, d = 0, 1
        for char in s:
            rows[idx].append(char)
            if idx == 0:
                d = 1
            elif idx == len(rows)-1:
                d = -1
            idx += d


        res = ""
        for row in rows:
            res_row = "".join(row)
            res += res_row

        return res
```

---

## [26. Remove Duplicates from Sorted Array](https://leetcode.com/problems/remove-duplicates-from-sorted-array/description/?envType=study-plan-v2&envId=top-interview-150)

### Explaination

None

### Solution

```python
class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        p1 = 0 # unique num pointer
        for p in range(len(nums)):
            if nums[p1] != nums[p]:
                p1 += 1
                nums[p1] = nums[p]
        return p1 + 1
```

---

## [80. Remove Duplicates from Sorted Array II](https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/description/?envType=study-plan-v2&envId=top-interview-150)

### Explaination

None

### Solution

```python
class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        p1 = 1
        count = 1
        for p in range(1, len(nums)):
            if nums[p] == nums[p-1]:
                count += 1
            else:
                count = 1
            if count <= 2:
                nums[p1] = nums[p]
                p1 += 1

        return p1
```

---

## [189. Rotate Array](https://leetcode.com/problems/rotate-array/description/?envType=study-plan-v2&envId=top-interview-150)

### Explaination

None

### Solution

```python
class Solution:
    def rotate(self, nums: List[int], k: int) -> None:
        """
        Do not return anything, modify nums in-place instead.
        """

        n = len(nums) # n -> length
        k %= n # k -> steps

        self.reverse(nums, 0, n-1)
        self.reverse(nums, 0, k-1)
        self.reverse(nums, k, n-1)


    def reverse(self, nums: List[int], start: int, end: int) -> None:
        while start < end:
            nums[start], nums[end] = nums[end], nums[start]
            start, end = start+1, end-1
```

---

## [125. Valid Palindrome](https://leetcode.com/problems/valid-palindrome/description/?envType=study-plan-v2&envId=top-interview-150)

### Explaination

None

### Solution

```python
class Solution:
    def isPalindrome(self, s: str) -> bool:
        if s == " ":
            return True
        # preprocessing
        seq = ''
        s = s.lower()
        for l in s:
            if l.isnumeric() or l.isalpha():
                seq += l
        # validating palindrome
        start, end = 0, len(seq)-1

        while start < end:
            if seq[start] != seq[end]:
                return False
            start, end = start+1, end-1

        return True
```

---

## [392. Is Subsequence](https://leetcode.com/problems/is-subsequence/description/?envType=study-plan-v2&envId=top-interview-150)

### Explaination

None

### Solution

```python
class Solution:
    def isSubsequence(self, s: str, t: str) -> bool:
        s_ptr, t_ptr = 0, 0

        while s_ptr < len(s) and t_ptr < len(t):
            if s[s_ptr] == t[t_ptr]:
                s_ptr += 1
            t_ptr += 1
        return s_ptr == len(s)
```

---

## [36. Valid Sudoku](https://leetcode.com/problems/valid-sudoku/description/?envType=study-plan-v2&envId=top-interview-150)

### Explaination

None

### Solution

```python
class Solution:
    def isValidSudoku(self, board: List[List[str]]) -> bool:
        row = [set() for _ in range(9)]
        col = [set() for _ in range(9)]
        mx = [[set() for _ in range(3)] for _ in range(3)]

        for r in range(9):
            for c in range(9):

                cur = board[r][c]

                if cur == ".":
                    continue

                # check row
                if cur in row[c]:
                    return False
                else:
                    row[c].add(cur)

                if cur in col[r]:
                    return False
                else:
                    col[r].add(cur)

                if cur in mx[r//3][c//3]:
                    return False
                else:
                    mx[r//3][c//3].add(cur)

        return True
```

---

## [54. Spiral Matrix](YOUR_URL)

### Explaination

None

### Solution

```python

```

---

## [Question](YOUR_URL)

### Explaination

None

### Solution

```python

```

---

## [Question](YOUR_URL)

### Explaination

None

### Solution

```python

```

---

## [Question](YOUR_URL)

### Explaination

None

### Solution

```python

```

---

## [Question](YOUR_URL)

### Explaination

None

### Solution

```python

```

---

## [Question](YOUR_URL)

### Explaination

None

### Solution

```python

```

---

## [Question](YOUR_URL)

### Explaination

None

### Solution

```python

```

---

## [Question](YOUR_URL)

### Explaination

None

### Solution

```python

```

---

## [Question](YOUR_URL)

### Explaination

None

### Solution

```python

```

---

## [Question](YOUR_URL)

### Explaination

None

### Solution

```python

```

---

## [Question](YOUR_URL)

### Explaination

None

### Solution

```python

```

---

## [Question](YOUR_URL)

### Explaination

None

### Solution

```python

```

---

## [Question](YOUR_URL)

### Explaination

None

### Solution

```python

```

---

## [Question](YOUR_URL)

### Explaination

None

### Solution

```python

```

---

## [Question](YOUR_URL)

### Explaination

None

### Solution

```python

```