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'''#2.1 Write code to remove duplicates from an unsorted linked list.
FOLLOW UP
How would you solve this problem if a temporary buffer is not allowed?'''
from llist import sllist

def remove_dubs(l):
    

    if l.first is None:
        raise ValueError ('list is empty')
    
    current  = l.first
    seen=set([current.value])
    while current.next:
        if current.next.value in seen:
            current.next = current.next.next
        else:
            seen.add(current.next.value)
            current = current.next
    return seen


    

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l=sllist([1,2,3,3])
node = l.first
node.next.next()


    

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remove_dubs(l)


    

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#2.2 Implement an algorithm to find the nth to last element of a singly linked list.


    

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def kthtolast(l,k):
    
    if l.first is None:
        return 
    
    runner = current = l.first
    for i in range (k):
        if runner is None:
            return None
        runner = runner.next
        
    while runner:
        current=current.next
        runner = runner.next
    
    return current


    

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l=sllist([1,2,3,3])
kthtolast(l,3)


    

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#2.3 Implement an algorithm to delete a node in the middle of a single linked list, given only access to that node.


    

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def delete_middle_node(node):
    node.value=node.next.value
    node.next=node.next.next


    

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l=llist([1,2,3,3])
delete_middle_node(l)


    

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#2.4 You have two numbers represented by a linked list, where each node contains a single digit. The digits are stored in reverse order, such that the 1’s digit is at the head of the list. Write a function that adds the two numbers and returns the sum as a linked list.


    

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import itertools
def maxtime(arr):
    res=[]
    arr=sorted(arr)
    for i in itertools.permutations(arr):
        if i[0]<=2:
            if i[2]<6:        
                res.append(i)
        #else:
            #raise ValueError('cannt do it')

    ti = res[-1]
    t = str(ti[0])+''+str(ti[1])+':'+str(ti[2])+''+str(ti[3])
                
    return t,res


    

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maxtime([4,7,5,1])


    

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a=[[1,1,1,2],
[1,9,1,2],
[1,8,9,2],
[1,2,3,4]]


    

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a


    

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def cavityMap(arr):
    
    n=int(arr[0])
    for i in range(1,n-1):
        for j in range(1,n-1):
            if arr[i-1][j] != 'X' and int(arr[i-1][j]) < int(arr[i][j]) and \
                arr[i+1][j] != 'X' and int(arr[i+1][j]) < int(arr[i][j]) and \
                arr[i][j-1] != 'X' and int(arr[i][j-1]) < int(arr[i][j]) and \
                arr[i][j+1] != 'X' and int(arr[i][j+1]) < int(arr[i][j]):
                    arr[i][j] = 'X'
    return arr


    

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n = int(input())
arr=[]

for k in range(n):
    line = list(input())
    arr.append(line)
    
#cavityMap(arr)

print (''.join(l))
arr


    

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cavityMap(a)


    

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# Complete the function below.

def cavityMap(arr):
    
    for i in arr:
        i=int(i)
    n=len(arr[0])
    

    for i in range(1,n-1):
        for j in range(1,n-1):
            cur = int(arr[i][j])
            left = int(arr[i][j-1])
            right = int(arr[i][j+1])
            top = int(arr[i-1][j])
            bottom = int(arr[i+1][j])

            if(cur>left and cur>right and cur> top and cur>bottom):
                arr[i][j] = int(arr[i][j])
                arr[i][j] = 'X'

    return (arr)


    

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