23.04.10 Today’s Leetcode

20. Valid Parentheses (easy)

with Stack

class Solution:
    def isValid(self, s: str) -> bool:
        stack = []
        open_ = '({['
        close_ = ']})'
        for p in s:
            if p in open_:
                stack.append(p)
            if p in close_:
                c = ''
                if stack:
                    c = stack.pop()
                if c == '[' and p == ']':
                    continue
                if c == '(' and p == ')':
                    continue
                if c == '{' and p == '}':
                    continue
                return False
        return len(stack) == 0

2337. Move Pieces to Obtain a String (medium), 777. Swap Adjacent in LR String (medium)

Two problems are exactly equal

class Solution:
    def canChange(self, start: str, target: str) -> bool:

        m = [char for char in start if char != '_']
        n = [char for char in target if char != '_']
        if m != n:
            return False

        def help(s):
            pos_l, pos_r = [], []
            for index, char in enumerate(s):
                if char == 'L':
                    pos_l.append(index)
                if char == 'R':
                    pos_r.append(index)
            return pos_l, pos_r
        
        a, b = help(start)
        c, d = help(target)
        if len(a) != len(c) or len(b) != len(d):
            return False
        for i in range(len(a)):
            if c[i] > a[i]:
                return False
        for i in range(len(b)):
            if d[i] < b[i]:
                return False
        return True
        

332. Remove Palindromic Subsequences (easy)

class Solution:
    def removePalindromeSub(self, s):
        return 2 - (s == s[::-1]) - (s == "")