O(log N) 방법

def square(n):
    if n == 0:
        return 0

    # Handle negative number
    if n < 0:
        n = -n

    # Get floor (n/2) using right shift
    x = n >> 1

    # If n is odd
    if n & 1:
        return ((square(x) << 2) + (x << 2) + 1)

    # If n is even
    else:
        return (square(x) << 2)

# Driver Code
for n in range(1,6):
    print("n = {}, n^2 = {}".format(n, square(n)))

Reference

Calculate square of a number without using *, / and pow() - GeeksforGeeks