pascDiagFast.py

from fractions import Fraction
def pascDiagFast(row,length):

	#compute the fractions of this diag
	fracs=[1]*(length)
	for i in range(length-1):
		num = i+1
		denom = row+1+i
		fracs[i] = Fraction(num,denom)

	#now let's compute the values
	vals=[0]*length

	#first figure out the leftmost tail of this diag
	lowRow = row + (length-1)
	lowRowCol = row
	tail = pascalIndexInRowFast(lowRow,lowRowCol)

	vals[-1] = tail

	#walk backwards!
	for i in reversed(range(length-1)):
		vals[i] = int(fracs[i]*vals[i+1])

	return vals