go: add «2116. Check if a Parentheses String Can Be Valid»

URL:	https://leetcode.com/problems/check-if-a-parentheses-string-can-be-valid/
Signed-off-by: Matej Focko <me@mfocko.xyz>

go/check-if-a-parentheses-string-can-be-valid.go

@@ -0,0 +1,44 @@
+package main
+
+func canBeValid(s string, locked string) bool {
+	n := len(s)
+	if n%2 == 1 {
+		// can't pair brackets
+		return false
+	}
+
+	open, unlocked, balance := 0, 0, 0
+	for i := range n {
+		if locked[i] == '0' {
+			unlocked++
+		} else if s[i] == '(' {
+			open++
+		} else if s[i] == ')' {
+			if open > 0 {
+				open--
+			} else if unlocked > 0 {
+				unlocked--
+			} else {
+				return false
+			}
+		}
+	}
+
+	for i := n - 1; i >= 0 && (unlocked != 0 || open != 0); i-- {
+		if locked[i] == '0' {
+			balance--
+			unlocked--
+		} else if s[i] == '(' {
+			balance++
+			open--
+		} else if s[i] == ')' {
+			balance--
+		}
+
+		if balance > 0 {
+			return false
+		}
+	}
+
+	return open <= 0
+}