common_element.py

def findCommon(ar1, ar2, ar3, n1, n2, n3): 
    i, j, k = 0, 0, 0
    # Iterate through three arrays while all arrays have elements
    while (i < n1 and j < n2 and k < n3):
        if (ar1[i] == ar2[j] and ar2[j] == ar3[k]):

            print ar1[i],

            i += 1

            j += 1

            k += 1
        elif ar1[i] < ar2[j]:

            i += 1
 

        # y < z

        elif ar2[j] < ar3[k]:

            j += 1
 

        # We reach here when x > y and z < y, i.e., z is smallest

        else:

            k += 1
 
 
# Driver program to check above function

ar1 = [1, 5, 10, 20, 40, 80]

ar2 = [6, 7, 20, 80, 100]

ar3 = [3, 4, 15, 20, 30, 70, 80, 120]

n1 = len(ar1)

n2 = len(ar2)

n3 = len(ar3)

print "Common elements are",
findCommon(ar1, ar2, ar3, n1, n2, n3)