LeetCode in Kotlin
22. Generate Parentheses
Medium
Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.
Example 1:
Input: n = 3
Output: [”((()))”,”(()())”,”(())()”,”()(())”,”()()()”]
Example 2:
Input: n = 1
Output: [”()”]
Constraints:
1 <= n <= 8
Solution
class Solution {
fun generateParenthesis(n: Int): List<String> {
val sb = StringBuilder()
val ans: MutableList<String> = ArrayList()
return generate(sb, ans, n, n)
}
private fun generate(sb: StringBuilder, str: MutableList<String>, open: Int, close: Int): List<String> {
if (open == 0 && close == 0) {
str.add(sb.toString())
return str
}
if (open > 0) {
sb.append('(')
generate(sb, str, open - 1, close)
sb.deleteCharAt(sb.length - 1)
}
if (close > 0 && open < close) {
sb.append(')')
generate(sb, str, open, close - 1)
sb.deleteCharAt(sb.length - 1)
}
return str
}
}