Question

How to find all common elements in given three sorted lists with Python

Answer 1

def PrintCommonElementsInThreelstays(lst1,  lst2,  lst3) :
    size1 = len(lst1)
    size2 = len(lst2)
    size3 = len(lst3)
        
    i = 0
    j = 0
    k = 0
    while (i < size1 and j < size2 and k < size3) :
        if (lst1[i] == lst2[j] and lst3[k] == lst1[i]) :
            print(str(lst1[i]) + " ", end ="")
            i += 1
            j += 1
            k += 1
        elif(lst1[i] < lst2[j]) :
            i += 1
        elif(lst2[j] < lst3[k]) :
            j += 1
        else :
            k += 1

lst1 = [2, 5, 6, 7, 9, 12, 20, 25, 30, 31]
lst2 = [4, 7, 10, 11, 20, 21, 30, 31, 37]
lst3 = [1, 2, 5, 7, 9, 18, 19, 20, 31, 32, 38, 39, 40, 50]

PrintCommonElementsInThreelstays(lst1, lst2, lst3)
    
 
 
 
'''
run:
 
7 20 31 

'''

 

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Answer 2

def PrintCommonElementsInThreelstays(lst1,  lst2,  lst3) :
    lst1 = set(lst1)
    lst2 = set(lst2)
    lst3 = set(lst3)
    
    common_elements = lst1 & lst2 & lst3
    
    print(common_elements)

lst1 = [2, 5, 6, 7, 9, 12, 20, 25, 30, 31]
lst2 = [4, 7, 10, 11, 20, 21, 30, 31, 37]
lst3 = [1, 2, 5, 7, 9, 18, 19, 20, 31, 32, 38, 39, 40, 50]

PrintCommonElementsInThreelstays(lst1, lst2, lst3)
    
 
 
 
'''
run:
 
{20, 7, 31}

'''

 

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