built-in sequence type exercise

Author: AstinCHOI

.DS_Store

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+def combinations(s):
+    if len(s) < 2:
+        return s
+    res = []
+    for i, c in enumerate(s):
+        res.append(c)
+        for j in combinations(s[:i] + s[i+1:]):
+            res.append(c + j)
+    return res
+
+if __name__ == '__main__':
+    result = combinations("abc")
+    print(result)

general_problems/.DS_Store

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+def is_palindrome(s):
+    l = s.split(' ')
+    s2 = ''.join(l)
+    return s2 == s2[::-1]
+
+def is_palindrome2(s):
+    l = len(s)
+    f, b = 0, l-1
+    while f < l // 2:
+        while s[f] == ' ':
+            f+=1
+        while s[b] == ' ':
+            b-=1
+        if s[f] != s[b]:
+            return False
+        f+=1
+        b-=1
+    return True
+
+def is_palindrome3(s):
+    s = s.strip()
+    if len(s) < 2:
+        return True
+    if s[0] == s[-1]:
+        return is_palindrome(s[1:-1])
+    else:
+        return False
+
+if __name__ == '__main__':
+    str1 = "subi no onibus"
+    str2 = ""
+    str3 = "hello"
+    print(is_palindrome(str1))
+    print(is_palindrome(str2))
+    print(is_palindrome(str3))
+    print(is_palindrome2(str1))
+    print(is_palindrome2(str2))
+    print(is_palindrome2(str3))
+    print(is_palindrome3(str1))
+    print(is_palindrome3(str2))
+    print(is_palindrome3(str3))

general_problems/arrays_strings_lists/combination.py

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+def perm(s):
+    if len(s) < 2:
+        return s
+    res = []
+    for i, c in enumerate(s):
+        for cc in perm(s[i+1:] + s[:i]):
+           res.append(c + cc)
+    return res
+
+if __name__ == '__main__':
+    result = perm("123")
+    print(result)

general_problems/arrays_strings_lists/palindrome.py

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+def revert(s):
+    if s:
+        s = s[-1] + revert(s[:-1])
+    return s
+
+def revert2(string):
+    return string[::-1]
+
+if __name__ == '__main__':
+    str1 = "Hello World!"
+    str2 = revert(str1)
+    str3 = revert2(str1)
+    print(str2)
+    print(str3)

general_problems/arrays_strings_lists/permutation.py

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+def reverser(string1, p1=0, p2=None):
+    if len(string1) < 2:
+        return string1
+    p2 = p2 or len(string1)-1
+    while p1 < p2:
+        string1[p1], string1[p2] = string1[p2], string1[p1]
+        p1 += 1
+        p2 -= 1
+
+def reversing_words_setence_logic(string1):
+    # 먼저, 문장 전체를 반전한다.
+    reverser(string1)
+    # print(string1)
+    p = 0
+    start = 0
+    while p < len(string1):
+        if string1[p] == u"\u0020":
+            # 단어를 다시 반전한다(단어를 원위치로 돌려놓는다).
+            reverser(string1, start, p-1)
+            # print(string1)
+            start = p+1
+        p += 1
+    # 마지막 단어를 반전한다(단어를 원위치로 돌려놓는다).
+    reverser(string1, start, p-1)
+    # print(string1)
+    return ''.join(string1)
+
+
+if __name__ == '__main__':
+    str1 = "Buffy is a Vampire Slayer"
+    str2 = reversing_words_setence_logic(list(str1))
+    print(str2)

general_problems/arrays_strings_lists/reversing_string.py

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+def reverse_words_brute(string):
+    word, sentence = [], []
+    for character in string:
+        if character != ' ':
+            word.append(character)
+        else:
+            # 조건문에서 빈 리스트는 False다. 여러 공백이 있는 경우, 조건문을 건너뛴다.
+            if word:
+                sentence.append(''.join(word))
+            word = []
+
+    # 마지막 단어가 있다면, 문장에 추가한다.
+    if word != '':
+        sentence.append(''.join(word))
+    sentence.reverse()
+    return ' '.join(sentence)
+
+
+if __name__ == '__main__':
+    str1 = "Buffy is a Vampire Slayer"
+    str2 = reverse_words_brute(str1)
+    print(str2)

general_problems/arrays_strings_lists/reversing_words_1.py

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+def reversing_words_slice(word):
+    new_word = []
+    words = word.split(' ')
+    for word in words[::-1]:
+        new_word.append(word)
+    return ' '.join(new_word)
+
+
+if __name__ == '__main__':
+    str1 = "Buffy is a Vampire Slayer"
+    str2 = reversing_words(str1)
+    print(str2)

general_problems/arrays_strings_lists/reversing_words_2.py

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+def reversing_words(str1):
+    words = str1.split(' ')
+    rev_set = " ".join(reversed(words))
+    return rev_set
+
+def reversing_words2(str1):
+    words = str1.split(' ')
+    words.reverse()
+    return ' '.join(words)
+
+
+if __name__ == '__main__':
+    str1 = "Buffy is a Vampire Slayer"
+    str2 = reversing_words(str1) 
+    str3 = reversing_words2(str1)
+    print(str2)
+    print(str3)