munguial

# https://leetcode.com/explore/challenge/card/30-day-leetcoding-challenge/529/week-2/3290/
class Solution:
    def middleNode(self, head: ListNode) -> ListNode:
        slow = head
        fast = head
        
        while fast:
            fast = fast.next
            if not fast:
                break

munguial

# https://leetcode.com/explore/featured/card/30-day-leetcoding-challenge/529/week-2/3291/
class Solution:
    def backspaceCompare(self, S: str, T: str) -> bool:
        a = len(S) - 1
        b = len(T) - 1
        
        skipA = 0
        skipB = 0
        
        while a >= 0 or b >= 0:

munguial

# https://leetcode.com/explore/featured/card/30-day-leetcoding-challenge/529/week-2/3292/

class MinStack:

    def __init__(self):
        self.stack = []
        self.minStack = []
        

    def push(self, x: int) -> None:

munguial

# https://leetcode.com/explore/challenge/card/30-day-leetcoding-challenge/529/week-2/3293/

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Result:

munguial

# https://leetcode.com/explore/featured/card/30-day-leetcoding-challenge/529/week-2/3297/
import java.util.Collections
import java.util.PriorityQueue

class Solution {
    fun lastStoneWeight(stones: IntArray): Int {
        val pq = PriorityQueue<Int>(Collections.reverseOrder())
        for (s in stones) {
            pq.add(s)
        }

munguial

class Solution:
    def findMaxLength(self, nums: List[int]) -> int:
        history = {0: -1}
        balance = 0
        res = 0
        
        for i in range(len(nums)):
            balance += 1 if nums[i] else -1
            
            if balance in history:

munguial

// https://leetcode.com/explore/featured/card/30-day-leetcoding-challenge/529/week-2/3299/

class Solution {
    fun stringShift(s: String, shift: Array<IntArray>): String {
        val singleShift: Pair<Int, Int> = calculateSingleShift(shift)
        return shiftCharacters(s, singleShift.first, singleShift.second % s.length)
    }
    
    fun shiftCharacters(s: String, direction: Int, n: Int): String {
        if (n == 0) {

munguial

// https://leetcode.com/explore/featured/card/30-day-leetcoding-challenge/530/week-3/3300/

class Solution {
    fun productExceptSelf(nums: IntArray): IntArray {
        var output = nums.copyOf()
        
        for (i in nums.lastIndex - 1 downTo 0) {
            output[i] *= output[i + 1]    
        }
        

munguial

# https://leetcode.com/explore/featured/card/30-day-leetcoding-challenge/530/week-3/3301/

class Solution:
    def checkValidString(self, s: str) -> bool:
        dp = {}
        return self.isValid(s, 0, 0, dp)
    
    def isValid(self, s: str, i: int, c: int, dp: dict) -> bool:
        if (i, c) in dp:
            return dp[i, c]

munguial

// https://leetcode.com/explore/challenge/card/30-day-leetcoding-challenge/530/week-3/3302/
class Solution {
    fun numIslands(grid: Array<CharArray>): Int {
        var result = 0
        for (row in grid.indices) {
            for (col in grid[0].indices) {
                if (grid[row][col] == '1') {
                    result += 1
                    dfs(grid, row, col)
                }