GuillermoPena · June 5, 2014 14:34 · Jun 5, 2014
diff --git a/checkio.3.01.brackets.py b/checkio.3.01.brackets.py
@@ -0,0 +1,36 @@
+# CheckIO - Electronic Station Challenge 1 : Brackets
+# http://checkio.org
+
+# You are given an expression with numbers, brackets and operators. 
+# For this task only the brackets matter. Brackets come in three flavors: "{}" "()" or "[]". 
+# Brackets are used to determine scope or to restrict some expression. 
+# If a bracket is open, then it must be closed with a closing bracket of the same type. 
+# The scope of a bracket must not intersected by another bracket. 
+# For this task, you should to make a decision to correct an expression or not based on the brackets. 
+# Do not worry about operators and operands.
+# Input: An expression with different of types brackets. A string (unicode).
+# Output: The correctness the expression or don’t. A boolean.
+# Precondition: There are only brackets ("{}" "()" or "[]"), digits or operators ("+" "-" "*" "/").
+
+def checkio(expression):
+    BRACKETS="()[]{}"
+    openBrackets=[]
+    for b in expression:
+        if BRACKETS.count(b)==0: continue   # No bracket character
+        if "([{".count(b): openBrackets+=b  # Adding open bracket
+        else:   # if char is a close bracket...
+            if not openBrackets: return False                   # Empty open brackets array case
+            lastBracketIndex=BRACKETS.index(openBrackets[-1])   
+            if b!=BRACKETS[lastBracketIndex+1]: return False    # Different type of bracket case
+            else: openBrackets=openBrackets[:-1]                # Removing bracket from array...
+    if openBrackets: return False                               # Some open bracket remaining case
+    return True
+
+#These "asserts" using only for self-checking and not necessary for auto-testing
+if __name__ == '__main__':
+    assert checkio("((5+3)*2+1)") == True, "Simple"
+    assert checkio("{[(3+1)+2]+}") == True, "Different types"
+    assert checkio("(3+{1-1)}") == False, ") is alone inside {}"
+    assert checkio("[1+1]+(2*2)-{3/3}") == True, "Different operators"
+    assert checkio("(({[(((1)-2)+3)-3]/3}-3)") == False, "One is redundant"
+    assert checkio("2+3") == True, "No brackets, no problem"