g0001_0100.s0032_longest_valid_parentheses.solution.rb Maven / Gradle / Ivy

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104 LeetCode algorithm problem solutions

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# #Hard #Top_100_Liked_Questions #String #Dynamic_Programming #Stack #Big_O_Time_O(n)_Space_O(1)
# #2023_11_19_Time_73_ms_(82.61%)_Space_211_MB_(100.00%)

# @param {String} s
# @return {Integer}
def longest_valid_parentheses(s)
  max = 0
  left = 0
  right = 0
  n = s.length
  ch = nil

  (0...n).each do |i|
    ch = s[i]
    if ch == '('
      left += 1
    else
      right += 1
    end

    if right > left
      left = 0
      right = 0
    end

    if left == right
      max = [max, left + right].max
    end
  end

  left = 0
  right = 0

  (n - 1).downto(0) do |i|
    ch = s[i]
    if ch == '('
      left += 1
    else
      right += 1
    end

    if left > right
      left = 0
      right = 0
    end

    if left == right
      max = [max, left + right].max
    end
  end

  max
end