Python

Python RSS

pascal triangle using lists

Please support our Python advertiser: Programming Forums - DaniWeb Sister Site

•

Join Date: Feb 2009

Posts: 2

Reputation: memphis1234 is an unknown quantity at this point

Solved Threads: 0

memphis1234 memphis1234 is offline

Offline

Newbie Poster

pascal triangle using lists

Feb 12th, 2009

I have to write a program which generates a pascal's triangle.
The user inputs the height of the triangle and it supposed to generate one.

This is what I have so far and I don't know how you would keep
adding rows after the second one. I'm so lost

 Help with Code Tags 
 python Syntax (Toggle Plain Text) 
numStr = raw_input("Please input the height of Pascal's Triangle: ")
row = int(numStr)
 
tri = []
 
row1 = [1]
row2 = [1, 1]
 
tri.append(row1)
tri.append(row2)
 
while len(tri) < row:
    print tri
    break
numStr = raw_input("Please input the height of Pascal's Triangle: ")
row = int(numStr)

tri = []

row1 = [1]
row2 = [1, 1]

tri.append(row1)
tri.append(row2)

while len(tri) < row:
    print tri
    break

•

Join Date: Feb 2009

Posts: 2

Reputation: memphis1234 is an unknown quantity at this point

Solved Threads: 0

memphis1234 memphis1234 is offline

Offline

Newbie Poster

Re: pascal triangle using lists

Feb 12th, 2009

updated. Not sure what I'm doing, though.

 Help with Code Tags 
 python Syntax (Toggle Plain Text) 
numStr = raw_input("Please input the height of Pascal's Triangle: ")
height = int(numStr)
 
tri = []
 
row1 = [1]
row2 = [1, 1]
tri.append(row1)
tri.append(row2)
 
while len(tri) < height:
    newRow = [1]
    oldRow = tri[-1]
    start = 0
    while start < (3-2):
        newRow.append(oldRow[start] + oldRow[1])
        start += 1
    newRow.append(1)
 
 
print tri
numStr = raw_input("Please input the height of Pascal's Triangle: ")
height = int(numStr)

tri = []

row1 = [1]
row2 = [1, 1]
tri.append(row1)
tri.append(row2)

while len(tri) < height:
    newRow = [1]
    oldRow = tri[-1]
    start = 0
    while start < (3-2):
        newRow.append(oldRow[start] + oldRow[1])
        start += 1
    newRow.append(1)
    

print tri

•

Join Date: Dec 2006

Posts: 1,045

Reputation: woooee is a jewel in the rough

Solved Threads: 294

woooee

Offline

Veteran Poster

Re: pascal triangle using lists

Feb 12th, 2009

You should increment height, otherwise it's an infinite loop. In general you want to use a for() or while() loop and append to a list on each loop. Add print statements to print what you don't get (especially 'height' and 'start').

Last edited by woooee; Feb 12th, 2009 at 11:43 pm.

•

Join Date: Oct 2006

Posts: 48

Reputation: yilmazhuseyin is an unknown quantity at this point

Solved Threads: 5

yilmazhuseyin yilmazhuseyin is offline

Offline

Light Poster

Re: pascal triangle using lists

Feb 13th, 2009

I can see two way to solve the problem
1) use two dimentional list.
2) use two one dimentional list to store current row and previous row.
(that is what you are doing.)

in your case you use only previous row to calculate current row. so in start, your previous row will be row 1 which stores only 1
and you calculate current row by using currentrow[i] = previousrow [i] + previous row[i-1] in a loop. (first element and last element in list are special cases.) after the loop you add currentrow to triangle list and make copy currentrow to previousrow and calculate next row.
I hope that would help.

Quick Reply to Thread

Show Printable Version

Other Threads in the Python Forum

Previous Thread: 'file' object is not callable
Next Thread: Designing a gui library for Python

Thread Tools	Search this Thread
Show Printable Version Email this Page

DaniWeb Message

Cancel Changes