1614. Maximum Nesting Depth of the Parentheses
Easy
A string is a valid parentheses string (denoted VPS) if it meets one of the following:
It is an empty string “”, or a single character not equal to “(” or “)”,
It can be written as AB (A concatenated with B), where A and B are VPS‘s, or
It can be written as (A), where A is a VPS.
We can similarly define the nesting depth depth(S) of any VPS S as follows:
depth(“”) = 0
depth(C) = 0, where C is a string with a single character not equal to “(” or “)”.
depth(A + B) = max(depth(A), depth(B)), where A and B are VPS‘s.
depth(“(” + A + “)”) = 1 + depth(A), where A is a VPS.
For example, “”, “()()”, and “()(()())” are VPS‘s (with nesting depths 0, 1, and 2), and “)(” and “(()” are not VPS‘s.
Given a VPS represented as string s, return the nesting depth of s.
Example 1:
Input: s = “(1+(2*3)+((8)/4))+1”
Output: 3
Explanation: Digit 8 is inside of 3 nested parentheses in the string.
Example 2:
Input: s = “(1)+((2))+(((3)))”
Output: 3
Constraints:
1 <= s.length <= 100
s consists of digits 0-9 and characters ‘+’, ‘-‘, ‘*’, ‘/’, ‘(‘, and ‘)’.
It is guaranteed that parentheses expression s is a VPS.
Solution:
/**
* @param String $s
* @return Integer
*/
function maxDepth($s) {
$ans = 0;
$opened = 0;
foreach(str_split($s) as $c) {
if ($c == ‘(‘) {
$opened += 1;
$ans = max($ans, $opened);
} elseif ($c == ‘)’) {
$opened -= 1;
}
}
return $ans;
}
}
