Question

Write a Python program to find the sum of Composite numbers between 1 to N. The value of N to be entered by the user.

Answer 1

Explanation:

Answer:

• The idea is to create an array of n elements and initialize them to 0 ( which makes this algorithm O(n) complex with respect to space too ).
• Now for every element index, mark its multiples so that they’re not evaluated. For example our current index is 2 so multiples would be 4,6,8,10...100 . At all these indexed, place a flag ( place value 1 at these indexes ) which will tell that this number is not prime OR it is composite.
• Move on to the next element (index) which happens to be 3 , now mark its multiples too. 6,9,12,...99 .
• If the current index flag is set (value = 1), don't evaluate it, skip to the next. For example : 4 will not be evaluated as it’s marked as 1, move on to the next that is 5 .

Answer 2

Explanation:

numr=int(input("Enter range:"))

print("Prime numbers:",end=' ')

for n in range(1,numr):

for i in range(2,n):

if(n%i==0):

break

else:

print(n,end=' ')

Hope it will help you Dear.