Created
December 28, 2018 03:58
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| def parentheses_combinations_brute_force_1(n): | |
| ans = [] | |
| def generate_all(candidate): | |
| if len(candidate) == 2 * n: | |
| if is_valid(candidate): | |
| ans.append(''.join(candidate)) | |
| else: | |
| candidate.append(')') | |
| generate_all(candidate) | |
| candidate.pop() | |
| candidate.append('(') | |
| generate_all(candidate) | |
| candidate.pop() | |
| generate_all([]) | |
| return ans | |
| def is_valid(candidate): | |
| opening_brackets = 0 | |
| closing_brackets = 0 | |
| for s in candidate: | |
| if s == '(': | |
| opening_brackets += 1 | |
| else: | |
| closing_brackets += 1 | |
| if closing_brackets > opening_brackets: | |
| return False | |
| return opening_brackets == closing_brackets | |
| def parentheses_combinations_with_backtracking(n): | |
| ans = [] | |
| def generate_all(candidate, o, c): | |
| print(candidate, o, c) | |
| if o == c and o + c == 2*n: | |
| ans.append(''.join(candidate)) | |
| else: | |
| if o + c < 2*n: | |
| if o < n: | |
| candidate.append('(') | |
| generate_all(candidate, o + 1, c) | |
| candidate.pop() | |
| if c < o: | |
| candidate.append(')') | |
| generate_all(candidate, o, c + 1) | |
| candidate.pop() | |
| generate_all([], 0, 0) | |
| return ans |
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