138 lines
3.6 KiB
Python
138 lines
3.6 KiB
Python
class SingleLinkedListNode(object):
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def __init__(self, value):
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self.value = value
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self.next = None
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def __repr__(self):
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nval = self.next and self.next.value or None
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return f"[{self.value}:{repr(nval)}]"
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class SingleLinkedList(object):
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def __init__(self):
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self.begin = None
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self.end = None
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def count(self):
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"""
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Returns number of items.
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Regresa la cantidad de ítems.
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"""
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count = 0
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node = self.begin
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while node:
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count += 1
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node = node.next
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return count
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def push(self, obj):
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"""
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Appends a new item on the end of the list.
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Añade un nuevo ítem al final de la lista.
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"""
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node = SingleLinkedListNode(obj)
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if self.begin is None:
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self.begin = node
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self.end = self.begin
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else:
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self.end.next = node
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self.end = node
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def pop(self):
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"""
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Removes the last item and returns its value.
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Remueve el último ítem y regresa su valor.
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"""
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if self.end is None:
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value = None
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elif self.end == self.begin:
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value = self.end.value
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self.end = self.begin = None
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else:
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node = self.begin
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while node.next != self.end:
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node = node.next
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value = node.next.value
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self.end = node
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self.end.next = None
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return value
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def unshift(self):
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"""
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Removes the first item and returns its value.
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Remueve el primer ítem y regresa su valor.
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"""
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if self.begin is None:
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value = None
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elif self.begin == self.end:
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value = self.begin.value
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self.begin = self.end = None
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else:
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value = self.begin.value
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self.begin = self.begin.next
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return value
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def shift(self, obj):
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"""
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Appends a new item on the begin of the list.
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Añade un nuevo ítem al inicio de la lista.
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"""
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node = SingleLinkedListNode(obj)
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if self.begin is None:
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self.begin = node
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self.end = self.begin
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else:
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curr, total = 0, self.count()
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self.push(node.value)
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while curr < total:
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self.push(self.unshift())
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curr += 1
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def remove(self, obj):
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"""
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Removes a item by its value and return its list index.
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Remueve un ítem según su valor y regresa su índice en la lista.
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"""
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count = 0
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node = self.begin
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while node.next:
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if obj == node.value:
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break
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count += 1
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node = node.next
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if node.next:
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node.value = node.next.value
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node.next = node.next.next
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else:
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node = None
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return count
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def get(self, index):
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"""
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Returns item value at list index.
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Regresa el valor del ítem en el índice de la lista.
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"""
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count = 0
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node = self.begin
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while count != index:
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count += 1
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node = node.next
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if node:
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return node.value
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else:
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return None
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def first(self):
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"""
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Returns value of first item.
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Regresa el valor del primer ítem.
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"""
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return self.begin.value
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def last(self):
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"""
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Returns value of last item.
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Regresa el valor del último ítem.
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"""
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return self.end.value
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