Suppose we have a string s containing brackets parenthesis "(" and ")", we have to find the length of the longest subsequence of balanced brackets.
So, if the input is like s = "())(()(", then the output will be 4, as we can take the subsequence like "()()"
To solve this, we will follow these steps −
res := 0
n := size of s
close := 0
for i in range n - 1 to 0, decrease by 1, do
if s[i] is same as ")", then
close := close + 1
otherwise,
if close > 0, then
close := close - 1
res := res + 2
return res
Let us see the following implementation to get better understanding −
Example
class Solution: def solve(self, s): res = 0 n = len(s) close = 0 for i in range(n - 1, -1, -1): if s[i] == ")": close += 1 else: if close > 0: close -= 1 res += 2 return res ob = Solution() s = "())(()(" print(ob.solve(s))
Input
"())(()("
Output
4