riverA = [[3,7], [3,9], [4,11], [6,12]]
riverB = [[12,4], [10,6], [6,7], [3,9], [2,4]]
riverC = [[12,4], [3,9], [2,4], [4,11]]

# Part 1 – more atomic way to define calculateLength()
def distance(a, b):
    return ((a[0] - b[0]) ** 2 + (a[1] - b[1]) ** 2) ** 0.5
    
def calculateLength(line):
    length = 0
    for i in range(len(line) - 1):
        length += distance(line[i], line[i+1])
    return length
    
# Part 1 – all in one function
def calculateLength(line):
    length = 0
    for i in range(len(line) - 1):
        length += ((line[i][0] - line[i+1][0]) ** 2 + (line[i][1] - line[i+1][1]) ** 2) ** 0.5
    return length

# Part 2
def findCommonPoints(line1, line2):
    commonPoints = []
    for point in line1:
        if point in line2:
            commonPoints.append(point)
    return commonPoints