I am fairly new to programming and have been learning some of the material through HackerRank. However, there is this one objective or challenge that I am currently stuck on. I've tried several things but still cannot figure out what exactly I am doing wrong.
Objective: Read N and output the numbers between 0 and N without any white spaces or using a string method.
N = int(input())
listofnum = []
for i in range(1, N +1):
listofnum.append(i)
print (*(listofnum))
Output :
1 2 3
N = int(input())
answer = ''
for i in range(1, N + 1):
answer += str(i)
print(answer)
This is the closest I can think of to 'not using any string methods', although technically it is using str.__new__/__init__/__add__ in the background or some equivalent. I certainly think it fits the requirements of the question better than using ''.join.
repr instead of str? str looks too much like "using a string method" to me.Without using any string method, just using integer division and list to reverse the digits, print them using sys.stdout.write:
import sys
N = int(input())
for i in range(1,N+1):
l=[]
while(i):
l.append(i%10)
i //= 10
for c in reversed(l):
sys.stdout.write(chr(c+48))
Or as tdelaney suggested, an even more hard-code method:
import os,sys,struct
N = int(input())
for i in range(1,N+1):
l=[]
while(i):
l.append(i%10)
i //= 10
for c in reversed(l):
os.write(sys.stdout.fileno(), struct.pack('b', c+48))
All of this is great fun, but the best way, though, would be with a one-liner with a generator comprehension to do that, using str.join() and str construction:
"".join(str(x) for x in range(1,N+1))
Each number is converted into string, and the join operator just concatenates all the digits with empty separator.
"".join is a builtin string method. Chris and Alex just pointed out to me. Its not a operator.str word in it.print(*[el for el in range(0, int(input())+1)], sep="")
chr still count as a string method? It calls str.__init__. struct.pack('b', c+48) may be called for here.char and string in python unlike C. The solution does the "heavy lifting" just like if you don't have access to integer to string conversion.You can print numbers inside the loop. Just use end keyword in print:
print(i, end="")
join. and see my answer (with the help of tdelaney): no strings attached :)Try ''.join([str(i) for i in range(N)])
"".join is a builtin string method. Chris and Alex just pointed out to me.One way to accomplish this is to append the numbers to a blank string.
out = ''
for i in range(N):
out += str(i)
print(out)
You can make use of print()'s sep argument to "bind" each number together from a list comprehension:
>>> print(*[el for el in range(0, int(input())+1)], sep="")
10
012345678910
>>>
join is a string method, no?
<built-in method join of str object at 0x10df76ab0>.You have to do a simple math to do this. What they expect to do is multiply each of your list elements by powers of ten and add them up on each other. As an example let's say you have an array; a = [2,3,5] and you need to output; 235
Then you multiply each of loop elements starting from right to left by 10^0, 10^1 and 10^2. You this code after you make the string list.
a = map(int,a)
for i in range(len(a)):
sum += (10**i)*a[-i]
print sum
You are done!
total = 0; for i in range(n):; total = total * 10 + i). Second, we weren't given a limit on what N could be. This idea works for digits, but what if we need to output the numbers 0 to 11? The algorithm won't generate 01234567891011.
print(i, end="")