detectValidExpressionBracketsMatch

detectValidExpressionBracketsMatch

"""

MATCH BRACKETS

"""

"""

BAM:  dynamic STACK - append opens, then match-pop on closes 
      DICT to match CLOSE to OPEN (as BACK-MATCH), 
            used as SET to filter non-parens
      SET to filter opens and ignore non-parens
      
ROBUST:  isValid = False by DEFAULT, break out
            
ATTN:  pop() correction to simulate peek()
       don't care about non-brackets!
"""

def checkMatch(expr):
    
    # default 
    isValid = False
    
    close_matches = { 
                        ')':'(', 
                        '}':'{',
                        ']':'['
                    }
              
    opens = { '(', '{', '[' }
              
    stack = []
    
    # - load LIFO Stack open
    # - skip non-parens; as don't care
    # - POP on closes as match on-the-fly
    # - MOVEON!
    
    # skip chars or non-brackets as don't care
    for aChar in expr:
        # IGNORE chars, or non-brackets
        if aChar in opens:
            stack.append(aChar)
        elif aChar in close_matches:
            # simulate peek
            peekTop = stack.pop()
            # print(peekTop)
            if (peekTop == close_matches[aChar]):
                # good match, prior pop good for match!
                isValid = True
                pass
            else:
                # NO match, FALSE expression, break out!
                # print("BREAK!")
                break
        else:
            # don't care
            pass
            
    print(stack)
    
    # if you have unmatched brackets leftover        
    if not stack:
        return isValid
    else:
        return isValid
        
        

# TRUE
# isMatch = checkMatch("")
# TRUE
# isMatch = checkMatch("ab")
# TRUE
# isMatch = checkMatch("({})")
# FALSE
# isMatch = checkMatch("(a{bc}")
# FALSE - FUCK!
isMatch = checkMatch("{)")

print(isMatch)