1106

Author: theforestvn88

1101-1200/1106_parsing_a_boolean_expression.rb

@@ -0,0 +1,25 @@
+# @param {String} expression
+# @return {Boolean}
+def parse_bool_expr(expression)
+    parse = lambda { |expression, index|
+        if expression[index] == 't'
+            return true, index + 1
+        elsif expression[index] == 'f'
+            return false, index + 1
+        elsif expression[index] == '!'
+            bool, next_index = parse.call(expression, index + 2)
+            return !(bool), next_index + 1
+        else
+            result = is_and = expression[index] == '&'
+            next_index = index + 2
+            while expression[next_index] != ')'
+                sub_result, next_index = parse.call(expression, next_index)
+                result = is_and ? (result & sub_result) : (result | sub_result)
+                next_index += 1 if expression[next_index] == ","
+            end
+            return result, next_index + 1
+        end
+    }
+
+    parse.call(expression, 0).first
+end