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Python: Valid String Closures.
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| """ | |
| Return TRUE or FALSE whether the string has valid closures. | |
| A valid closure can be: () or ({}) or []({}). | |
| An invalid closure interrupts open/close characters. | |
| Each opener character must have a closer character. | |
| Each closer character must have an opener character. | |
| """ | |
| patterns = { | |
| '{': '}', | |
| '[': ']', | |
| '(': ')', | |
| } | |
| def validPattern(str): | |
| invalid = False | |
| lis = list(str) | |
| openers = list(patterns.keys()) | |
| closers = list(patterns.values()) | |
| o = [] | |
| c = [] | |
| for i, char in enumerate(lis): | |
| o.append(char) if char in openers else None | |
| c.append(char) if char in closers else None | |
| try: | |
| prev = lis[i - 1] | |
| ahead = lis[i + 1] | |
| openIndex = openers.index(prev) if prev in openers else None | |
| closeIndex = closers.index(ahead) if ahead in closers else None | |
| if prev in openers and ahead in closers and openIndex == closeIndex: invalid = True | |
| except IndexError: pass | |
| except Exception as e: print(e) | |
| if invalid: return False | |
| return False if len(o) != len(c) else True | |
| print(validPattern('{([])}')) # True | |
| print(validPattern('[]{()}')) # True | |
| print(validPattern('{()}[]')) # True | |
| print(validPattern('[)]')) # False | |
| print(validPattern('{[]}(')) # False | |
| print(validPattern('}[]')) # False | |
| print(validPattern('{[]')) # False | |
| print(validPattern('{[(])]}')) # False | |
| print(validPattern('[(])')) # False |
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