4주차 실습-(2)

###################
def double(n):
    return n * 2

def halve(n):
    return n // 2
###################

def mult1(m,n):
    def loop(n,ans):
        if n > 0:
            return loop(n-1,ans+m)
        else:
            return ans
    return loop(n,0)

def mult2(m,n):
    ans = 0
    while n > 0:
        n -= 1
        ans += m
    else:
        return ans

def fastmult1(m,n):
    if n > 0:
        if n % 2 == 0:
            return fastmult1(double(m),halve(n))
        else:
            return m + fastmult1(m,n-1)
    else:
        return 0

def fastmult2(m,n):
    def loop(m,n,ans):
        if n > 0:
            if n % 2 == 0:
                return loop(double(m),halve(n),ans)
            else:
                return loop(m,n-1,ans+m)
        else:
            return ans
    return loop(m,n,0)

def fastmult3(m,n):
    ans = 0
    while n > 0:
        if n % 2 == 0:
            m, n = double(m), halve(n)
        else:
            n -= 1
            ans += m
    return ans

def russianmult1(m,n):
	def loop(m,n):
		if n > 1:
			if n % 2 != 0:
				return m + russianmult1(double(m),halve(n))
			else:
				return loop(double(m),halve(n))
		else: # n = 1;
			return m
	if n > 0:
		return loop(m,n)
	else:
		return 0

def russianmult2(m,n):
    def loop(m,n,ans):
        if n > 1:
            if n % 2 != 0:
                return loop(double(m),halve(n),ans+m)
            else:
                return loop(double(m),halve(n),ans)
        if n > 0:
            return ans + m
        else:
            return 0
    return loop(m,n,0)

def russianmult3(m,n):
    ans = 0
    while n > 1:
        if n % 2 != 0:
            m, n, ans = double(m), halve(n), ans+m
        else:
            m , n = double(m), halve(n)
    if n > 0:
        return ans + m


print(mult1(52,31))
print(mult2(31,37))
print(fastmult1(22,17))
print(fastmult2(61,29))
print(fastmult3(74,46))
print(russianmult1(41,25))
print(russianmult2(66,18))
print(russianmult3(29,31))