Created
February 7, 2020 19:47
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linked list python gist
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class Node(object): | |
def __init__(self,val): | |
self.val = val | |
self.next = None | |
def get_data(self): | |
return self.val | |
def set_data(self,val): | |
self.val = val | |
def get_next(self): | |
return self.next | |
def set_next(self,next): | |
self.next = next | |
class LinkedList(object): | |
def __init__(self,*values): | |
self.count = len(values) -1 | |
self.head = Node(values[0]) | |
node = self.head | |
for idx, val in enumerate(values): | |
if idx == 0: | |
continue | |
else: | |
tempnode = Node(val) | |
node.set_next(tempnode) | |
node = node.get_next() | |
def get_count(self): | |
return self.head | |
def insert(self,data): | |
new_node = Node(data) | |
new_node.set_next(self.head) | |
self.head = new_node | |
self.count +=1 | |
def insert_at(self,idx,val): | |
if idx > self.count +2: | |
return | |
if idx == 0: | |
self.insert(val) | |
else: | |
tempIdx = 0 | |
node = self.head | |
while tempIdx < idx -1: | |
node = node.get_next() | |
tempIdx += 1 | |
continuation = node.get_next() | |
insertion = Node(val) | |
node.set_next(insertion) | |
node.get_next().set_next(continuation) | |
self.count += 1 | |
def find(self,val): | |
item = self.head | |
while item != None: | |
if item.get_data() == val: | |
return item | |
else: | |
item = item.get_next() | |
return None | |
def deleteAt(self,idx): | |
if idx > self.count+1: | |
return | |
if idx == 0: | |
self.head = self.head.get_next() | |
else: | |
tempIdx = 0 | |
node = self.head | |
while tempIdx < idx -1: | |
node = node.get_next() | |
tempIdx +=1 | |
node.set_next(node.get_next().get_next()) | |
self.count -= 1 | |
def dump_list(self): | |
tempnode = self.head | |
while (tempnode != None): | |
print("Node: ",tempnode.get_data()) | |
tempnode = tempnode.get_next() | |
def swap(self,idx_a,idx_b): | |
if idx_a == idx_b: | |
return | |
elif idx_a > idx_b: | |
idx_2,idx_1 = idx_a,idx_b | |
else: | |
idx_2,idx_1 = idx_b,idx_a | |
node = self.head | |
tempIdx = 0 | |
while tempIdx < idx_2: | |
if tempIdx != idx_1: | |
node = node.get_next() | |
tempIdx += 1 | |
else: | |
elem_1 = node.get_data() | |
node = node.get_next() | |
tempIdx += 1 | |
elem_2 = node.get_data() | |
self.deleteAt(idx_1) | |
self.deleteAt(idx_2-1) | |
self.insert_at(idx_1,elem_2) | |
self.insert_at(idx_2,elem_1) | |
def move_min(self,sorted_idx): | |
temp_idx = 0 | |
node = self.head | |
selection = self.head.get_data() | |
while temp_idx <= self.count: | |
if temp_idx <= sorted_idx: | |
node = node.get_next() | |
temp_idx += 1 | |
elif temp_idx == sorted_idx +1: | |
selection = node.get_data() | |
selected_idx = temp_idx | |
node = node.get_next() | |
temp_idx += 1 | |
else: | |
if node.get_data() < selection: | |
selection = node.get_data() | |
selected_idx = temp_idx | |
try: | |
node = node.get_next() | |
temp_idx +=1 | |
except: | |
break | |
self.deleteAt(selected_idx) | |
self.insert_at(sorted_idx, selection) | |
return sorted_idx + 1 | |
def selection_sort(self): | |
""" | |
Note, move_min() method assumes that the element at first index is already sorted. As such, after | |
iteratively calling move_min(), the first element will be moved to the final index. Logic must be | |
built in to ID the final element and move it to its appropriate home. | |
""" | |
# part 1: sorts elements, pushing first element to last position | |
sorted_idx = 0 | |
while sorted_idx < self.count: | |
sorted_idx = self.move_min(sorted_idx) | |
# part 2: identifies final element and relocates appropriately | |
temp_idx = 0 | |
node = self.head | |
while temp_idx < self.count: | |
node = node.get_next() | |
temp_idx += 1 | |
final_elem = node.get_data() | |
final_idx = temp_idx | |
temp_idx = 0 | |
node = self.head | |
while temp_idx < self.count: | |
if node.get_data() < final_elem: | |
temp_idx += 1 | |
node = node.get_next() | |
else: | |
self.deleteAt(final_idx) | |
self.insert_at(temp_idx,final_elem) | |
break | |
if __name__ == '__main__': | |
t1 = LinkedList(4,2,1,0,3) | |
t1.selection_sort() | |
t1.dump_list() |
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