Reason for result of output of Python code

Question

why the while loop is executing more times than expected in printing a pascal triangle? every time the while loop is executed x is incremented by 1 whereas n remains the same I just started learning python please help

memo = {0:1}
def fac(n):
    if n not in memo:
        memo[n] = n*fac(n-1)
        return memo[n]
    else:
        return memo[n]

def pascal(x, space):
    while(x <= n):
        for j in range(space):
            print(" ", end = "")
        for i in range(0, x+1):
            print ( int(fac(x)/(fac(i)*fac(x-i))), end = " " )
        print("\n", end = "")
        x += 1
        space -= 1
        pascal(x, space)

n = eval(input())
space = n
x = 0
pascal(x, space)

what memo has to do with it? Function of memo is just to calculate factorial and store it respectively in a dictionary @AzatIbrakov — anonymous, May 23 '17 at 11:06
you probably should use [factorial](https://docs.python.org/2/library/math.html#math.factorial) — Azat Ibrakov, May 23 '17 at 11:11
whats wrong in using memo? just applying dynamic programming @AzatIbrakov — anonymous, May 23 '17 at 11:12
btw @AzatIbrakov I checked it, using your way, gives the same output — anonymous, May 23 '17 at 11:17
remove inner recursive call `pascal(x, space)` and it will work — Azat Ibrakov, May 23 '17 at 11:19

score 0 · Accepted Answer · answered May 23 '17 at 11:19

You are using two methods to iterate through the numbers in the pascal function, a while loop, and a recursive call. You just need one of them.

Keeping the while loop:

def pascal(x, space):
    while(x <= n):
        for j in range(space):
            print(" ", end = "")
        for i in range(0, x+1):
            print ( int(fac(x)/(fac(i)*fac(x-i))), end = " " )
        print("\n", end = "")
        x += 1
        space -= 1

Keeping the recursive call, turning the while into an if:

def pascal(x, space):
    if(x <= n):
        for j in range(space):
            print(" ", end = "")
        for i in range(0, x+1):
            print ( int(fac(x)/(fac(i)*fac(x-i))), end = " " )
        print("\n", end = "")
        x += 1
        space -= 1
        pascal(x, space)

Given 3 as input, both versions print the following:

Reason for result of output of Python code

1 Answers1