I'm writing a short snippet for a class that is supposed to run through a given list of numbers and append any primes. Right now it is returning all numbers in the range though.
I've found examples online for how to do this, but wanted to try it myself but I've seem to hit a wall... Here is my code:
from random import randrange
from time import sleep
def prime():
user_num = eval(input("Input a number: "))
list_prime = []
for i in range(2,user_num):
if (i % 2) == 1 and\
(i % 3) == 1 and\
(i % 4) == 1 and\
(i % 5) == 1 and\
(i % 6) == 1 and\
(i % 7) == 1 and\
(i % 8) == 1 and\
(i % 9) == 1 or\
i == 2:
list_prime.append(i)
if list_prime == '':
print('No prime numbers.')
if list_prime != '':
print('\nPrime numbers from 1 to ' + str(user_num) + ': ' + str(list_prime))
sleep(1)
print('\nClosing console in 60 seconds...')
sleep(60)
prime()
As he said, you werent correctly checking for prime numbers.
from random import randrange
from time import sleep
list_prime = []
user_num = 0
def prime():
user_num = eval(input("Input a number: "))
for i in range(2,user_num):
j = 2
isprime = 1
while (j <= i/2):
if (i % j == 0):
isprime = 0
break
j+=1
if (isprime == 1):
list_prime.append(i)
prime()
if list_prime == '':
print('No prime numbers.')
if list_prime != '':
print('\nPrime numbers from 1 to ' + str(user_num) + ': ' + str(list_prime))
sleep(1)
print('\nClosing console in 60 seconds...')
sleep(60)
Checking if the result of a modulo operation is 1 is not the correct approach. For example, 6 % 5 is 1, but 6 definitely isn't a prime number. Instead, for each suspect N you should check that no number X exists such that N % X == 0.
A wildly sub-optimal implementation could look like this:
list_prime = []
for i in range(2, user_num):
if all(n % x for x in list_prime):
list_prime.append(i)
Related
#Here I define the user and cpu function
cpu_num = random.randint(1,6)
user_selection = ["Odd", "Even"]
def cpu_choice():
choice = random.randint(1,6)
print("The computer's choice is",choice)
return choice
def user_choice():
while(True):
choice = input("Odd or Even? ")
if choice in user_selection:
print("Your choice is",choice)
return choice
else:
print("You did not write your answer correctly, please try again.")
#In this function I define the result of each round based on previous formulas and two new variables (num_rounds and user_lives) and everything works well
def round_result():
num_rounds = 0
user_lives = 10
while num_rounds < 8 and user_lives > 0:
user_pick = user_choice()
cpu_pick = cpu_choice()
if (cpu_pick % 2 == 0) and (user_pick == "Even"):
print (f'You have {user_lives + cpu_pick} lives left')
num_rounds += 1
user_lives = user_lives + cpu_pick
if (cpu_pick % 2 == 0) and (user_pick == "Odd"):
print (f'You have {user_lives - cpu_pick} lives left')
num_rounds += 1
user_lives = user_lives - cpu_pick
if (cpu_pick % 2 != 0) and (user_pick == "Even"):
print (f'You have {user_lives - cpu_pick} lives left')
num_rounds += 1
user_lives = user_lives - cpu_pick
if (cpu_pick % 2 != 0) and (user_pick == "Odd"):
print (f'You have {user_lives + cpu_pick} lives left')
num_rounds += 1
user_lives = user_lives + cpu_pick
#Everything works well until here, I don't know what am I doing wrong in the winner function
def winner():
user_won = user_lives > 0 and num_rounds == 8
cpu_won = user_lives < 0
game = round_result()
while game:
if user_won is True:
print ('You won')
if cpu_won is True:
print ('Cpu won')
I have written a simple code to print the largest prime factor of a given number from Project Euler. It works just fine for numbers like 24, but there is no response from the python shell for large numbers!
a=600851475143
b=[]
for i in range(2,600851475143):
if a%i==0:
if i==2:
b.append(i)
continue
for j in range(2,i+1):
if j==i:
b.append(i)
if i%j==0:
break
print(max(b))
print(b)
You can use an algorithm like this to get large factors of prime numbers:
import math
def LLL(N):
p = 1<<N.bit_length()-1
if N == 2:
return 2
if N == 3:
return 3
s = 4
M = pow(p, 2) - 1
for x in range (1, 100000):
s = (((s * N ) - 2 )) % M
xx = [math.gcd(s, N)] + [math.gcd(s*p+x,N) for x in range(7)] + [math.gcd(s*p-x,N) for x in range(1,7)]
try:
prime = min(list(filter(lambda x: x not in set([1]),xx)))
except:
prime = 1
if prime == 1:
continue
else:
break
return N/prime
I have been coding this problem for HackerRank and I ran into so many problems. The problem is called "Plus Minus" and I am doing it in Python 3. The directions are on https://www.hackerrank.com/challenges/plus-minus/problem. I tried so many things and it says that "there is no response on stdout". I guess a none-type is being returned. Here is the code.:
def plusMinus(arr):
p = 0
neg = 0
z = arr.count(0)
no = 0
for num in range(n):
if arr[num] < 0:
neg+=1
if arr[num] > 0:
p+=1
else:
no += 1
continue
return p/n
The following are the issues:
1) variable n, which represents length of the array, needs to be passed to the function plusMinus
2) No need to maintain the extra variable no, as you have already calculated the zero count. Therefore, we can eliminate the extra else condition.
3) No need to use continue statement, as there is no code after the statement.
4) The function needs to print the values instead of returning.
Have a look at the following code with proper naming of variables for easy understanding:
def plusMinus(arr, n):
positive_count = 0
negative_count = 0
zero_count = arr.count(0)
for num in range(n):
if arr[num] < 0:
negative_count += 1
if arr[num] > 0:
positive_count += 1
print(positive_count/n)
print(negative_count/n)
print(zero_count/n)
if __name__ == '__main__':
n = int(input())
arr = list(map(int, input().rstrip().split()))
plusMinus(arr, n)
The 6 decimals at the end are needed too :
Positive_Values = 0
Zeros = 0
Negative_Values = 0
n = int(input())
array = list(map(int,input().split()))
if len(array) != n:
print(f"Error, the list only has {len(array)} numbers out of {n}")
else:
for i in range(0,n):
if array[i] == 0:
Zeros +=1
elif array[i] > 0:
Positive_Values += 1
else:
Negative_Values += 1
Proportion_Positive_Values = Positive_Values / n
Proportion_Of_Zeros = Zeros / n
Proportion_Negative_Values = Negative_Values / n
print('{:.6f}'.format(Proportion_Positive_Values))
print('{:.6f}'.format(Proportion_Negative_Values))
print('{:.6f}'.format(Proportion_Of_Zeros))
I have solved euler problem 12, but it needs some optimization. I have read on the euler forums, but it has not helped me optimized it. However, I have managed to get the solution, I just need to speed it up. It currently takes 4 minutes to run. Here is my code:
import time
def nthtriangle(n):
return (n * (n + 1)) / 2
def numberofnfactors(n):
count = 0
if n==1:
return 1
for i in range(1, 1 + int(n ** 0.5)):
if n % i == 0:
count += 2
return count
def FirstTriangleNumberWithoverxdivisors(divisors):
found = False
counter = 1
while not found:
print(int(nthtriangle(counter)), " ", numberofnfactors(nthtriangle(counter)))
if numberofnfactors(nthtriangle(counter)) > divisors:
print(" first triangle with over ",divisors, " divisors is ", int(nthtriangle(counter)))
found = True
break
counter += 1
start_time = time.time()
FirstTriangleNumberWithoverxdivisors(500)
print("My program took", time.time() - start_time, "to run")
Instead of calculating each triangle number individually, use a generator to get the triangle numbers
from timeit import timeit
def triangle_numbers():
count = 1
num = 0
while True:
num += count
count += 1
yield num
def count_divisors(n):
count = 0
if n==1:
return 1
for i in range(1, 1 + int(n ** 0.5)):
if n % i == 0:
count += 2
return count
print(timeit('next(num for num in triangle_numbers() if count_divisors(num) >= 500)',
globals=globals(), number=1))
Gives me 3.8404819999996107 (seconds) on my machine. You could probably also improve the divisor counting.
What's really slowing you down is calling nthtriangle and numberoffactors more than once in your loop! Plus, those calls to print aren't free.
This code is to convert decimals to binary.
What I'm trying to do is to chop off the decimal part after diving by 2.
binary = []
n = 25
while n != 0:
binary.append(n % 2)
n = n / 2
int(n) #this part
print(binary)
print(n)
choose = input("continue?[Y/N]")
if choose == 'y':
continue
else:
break
print(list(reversed(binary)))
Is this what you want?
binary = []
n = 25
while n != 0:
binary.append(n % 2)
n = n / 2
n = int(n) #assign result to n
print(binary)
print(n)
choose = input("continue?[Y/N]")
if choose == 'y':
continue
else:
break
print(list(reversed(binary)))