|
| 1 | +let validExpressions, minimumRemoved, expression, input, length; |
| 2 | + |
| 3 | +/** |
| 4 | + * @param {string} s String containing parentheses (). |
| 5 | + * @return {string[]} List of all possible results. |
| 6 | + * @summary Remove Invalid Parentheses {@link https://leetcode.com/problems/remove-invalid-parentheses/} |
| 7 | + * @description Remove the minimum number of invalid parentheses in order to make the input string valid. |
| 8 | + * Space O(n) - on recurrsion maximum call stack depth will be n. |
| 9 | + * Time O(2^n) - each step can generate up to two more paths (remoeve or keep parentheses). |
| 10 | + */ |
| 11 | +const removeInvalidParentheses = s => { |
| 12 | + validExpressions = {}; |
| 13 | + minimumRemoved = Number.MAX_SAFE_INTEGER; |
| 14 | + expression = []; |
| 15 | + input = s; |
| 16 | + length = input.length; |
| 17 | + |
| 18 | + let openRemoveCount = 0; |
| 19 | + let closeRemoveCount = 0; |
| 20 | + for (let index = 0; index < length; index++) { |
| 21 | + if (s[index] === '(') openRemoveCount++; |
| 22 | + else if (s[index] === ')') { |
| 23 | + if (openRemoveCount === 0) closeRemoveCount++; |
| 24 | + if (openRemoveCount > 0) openRemoveCount--; |
| 25 | + } |
| 26 | + } |
| 27 | + |
| 28 | + removeMinimumParentheses(0, 0, 0, openRemoveCount, closeRemoveCount); |
| 29 | + |
| 30 | + return Object.keys(validExpressions); |
| 31 | +}; |
| 32 | + |
| 33 | +/** |
| 34 | + * @param {number} i Current index. |
| 35 | + * @param {number} openCount Number of open parentheses '(' for currently tested solution. |
| 36 | + * @param {number} closeCount Number of close parentheses ')' for currently tested solution. |
| 37 | + * @param {number} minOpen Remaining count of open parentheses to be removed for optimal solution. |
| 38 | + * @param {number} minClose Remaining count of close parentheses to be removed for optimal solution. |
| 39 | + * @return {undefined} Actual solution is written to validExpressions. |
| 40 | + */ |
| 41 | +const removeMinimumParentheses = (i, openCount, closeCount, minOpen, minClose) => { |
| 42 | + if (i === length && !minOpen && !minClose) { |
| 43 | + const solution = expression.join(''); |
| 44 | + validExpressions[solution] = true; |
| 45 | + } else if (i < length) { |
| 46 | + const char = input[i]; |
| 47 | + |
| 48 | + if (char === '(' && minOpen > 0) { |
| 49 | + removeMinimumParentheses(i + 1, openCount, closeCount, minOpen - 1, minClose); |
| 50 | + } |
| 51 | + if (char === ')' && minClose > 0) { |
| 52 | + removeMinimumParentheses(i + 1, openCount, closeCount, minOpen, minClose - 1); |
| 53 | + } |
| 54 | + |
| 55 | + expression.push(char); |
| 56 | + |
| 57 | + if (char !== '(' && char !== ')') { |
| 58 | + removeMinimumParentheses(i + 1, openCount, closeCount, minOpen, minClose); |
| 59 | + } else if (char === '(') { |
| 60 | + removeMinimumParentheses(i + 1, openCount + 1, closeCount, minOpen, minClose); |
| 61 | + } else if (closeCount < openCount) { |
| 62 | + removeMinimumParentheses(i + 1, openCount, closeCount + 1, minOpen, minClose); |
| 63 | + } |
| 64 | + |
| 65 | + expression.pop(); |
| 66 | + } |
| 67 | +}; |
0 commit comments