Create 15.lattice_paths

Python/15.lattice_paths

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+#Import factorial from math module
+from math import factorial
+
+#import time from time to calculate exection time
+from time import time
+
+#time at the start of execution
+start = time()
+
+#binomial coefficient function
+#https://en.wikipedia.org/wiki/Binomial_coefficient
+def nck(n,k):
+	#function which will return the binomial coefficient
+	#of n,k
+	return factorial(n)/(factorial(k)*factorial(n-k))
+
+#Number of lattice paths from (0,0) to (a,b) is given by
+#binomial coefficient C(a+b,a)
+print 'Number of lattice paths is: '+str(nck(20+20,20))
+
+#time at the end of program execution
+end = time()
+
+#Printing the total time
+print end-start