ds-algo-study/DS-n-Algos/Dynamic-Programming/popular-problems/LongestValidParentheses.js

Just experimenting with publishing a package

/*
  LeetCode -> https://leetcode.com/problems/longest-valid-parentheses/

  Given a string containing just the characters '(' and ')',
  find the length of the longest valid (well-formed) parentheses substring.
*/

const longestValidParentheses = ( s ) => {
  const n = s.length
  const stack = []

  // storing results
  const res = new Array( n ).fill( -Infinity )

  for ( let i = 0; i < n; i++ ) {
    const bracket = s[ i ]

    if ( bracket === ')' && s[ stack[ stack.length - 1 ] ] === '(' ) {
      res[ i ] = 1
      res[ stack[ stack.length - 1 ] ] = 1
      stack.pop()
    } else {
      stack.push( i )
    }
  }

  // summing all adjacent valid
  for ( let i = 1; i < n; i++ ) {
    res[ i ] = Math.max( res[ i ], res[ i ] + res[ i - 1 ] )
  }

  // adding 0 if there are none so it will return 0 instead of -Infinity
  res.push( 0 )
  return Math.max( ...res )
}

const main = () => {
  console.log( longestValidParentheses( ')()())' ) ) // output -> 4
  console.log( longestValidParentheses( '' ) ) // output -> 0
  console.log( longestValidParentheses( '(()' ) ) // output -> 2
}

main()