Python. Finde some numbers in range - for-loop

How to finde all numbers with 5 (for example) in the range(1,100) and change it on words?
for x in range(1,100):
(x % 5) == 0
del x
print("fff")
else:
print(x)
This code does not catch all values ​​with the number 5

Related

How to iterate over the digits of a number in MIPS?

I have a task where I need to take a number, e.g. 13002, and print it digit by digit using UART (including non-leading 0's). The UART expects that whatever it prints will go in the $s0 register but I can call it whenever I need using a jal.
This means I need to place a digit in $s0 and jump (the UART code has a jr $ra in it so it will return properly once complete.
My problem is I don't know how to iterate over the digits in the number.
My approach so far is to mod the number by 10 (Because it's a decimal number represented in binary) but that gives me the digits in reverse order.
E.g. 13002 % 10 = 2 (then divide 13002 by 10, integer division will truncate the decimal), 1300 % 10 = 0, divide again by 10, 130 ...so on and so forth.
As mentioned above however, that gives me the digits in reverse order. How would I properly iterate over the number?
I wrote some pseudocode in python but it's having trouble with numbers that have 0's in them:
def iterateOverDigits(n):
while (n >= 10):
x = n
i = 0
while (x >= 10):
x = x // 10
i += 1
print(x)
x = n
x = x % (10 ** i)
n = x
iterateOverDigits(1302) # This prints 132
In [1]: def by_digit(n):
...: for char in str(n):
...: print(char)
...:
In [2]: by_digit(120405)
1
2
0
4
0
5
In [3]:
Change the print statement to the following to remove the newlines between each digit:
print(char, end="")

How to find if X can be represented as the summation any Y distinct positive integers?

For example if
X= 10 , Y= 3
2,3,5 and 1,4,6 are possible
However for Y=10
This is not possible as we know we can't represent 10 as sum of 10 distinct positive integers.
Is there a more specific way to get the results?
Any X greater than or equal to S = 1 + 2 + ... + Y = Y*(Y+1)/2 can be so represented. Indeed,
X = 1 + 2 + ... + (Y-1) + (Y + X - S)
Any X smaller than S obviously cannot be.

Generate a random number which is far enough from another number

Let x, range, d be integers. We'd like to generate a number y, such that
1 <= y <= range
abs(x-y) >= d
One idea I came up with is to generate some smaller range and then make some adjustments to handle the numbers which too close to x. But that's really tedious.
Is there any better way to do it?
Here is a Python function that you should be able to adapt to the language of your choice:
import random
def distantRand(a,b,x,d):
#returns a random integer in range a ... b
#which is greater than or equal to d units from x
lb = max(a,x-d+1)
ub = min(b,x+d-1)
k = ub-lb+1 #number of numbers ruled out
if b-k < a:
return None
else:
y = random.randint(a,b-k)
if y > x - d:
y = y + k
return y
For example, distantRand(1,10,5,3) should return a number in the range 1 to 10 which is at least units away from 5. This rules out 3,4,5,6,7 as return values, leaving 10-5 = 5 valid numbers. The function picks one such in the range 1 to 5. If the number chosen is >2, 5 is added to it to make it a number which is >7 (but still <= 10). For example:
>>> for i in range(20):
print(distantRand(1,10,5,3))
1
1
1
8
2
9
10
8
1
10
10
2
8
10
8
8
8
2
1
2
I have done it like this in Python.
import random
range=100
d=20
x=115
while(True):
y=random.randint(1,range)
if abs(x-y)>=d:
print abs(x-y)
print y
break
And here it is as a def
import random
r=100
d=20
x=115
def yourandom (x,d,r):
while(True):
y=random.randint(1,r)
if abs(x-y)>=d:
print "abs(x-y)=",abs(x-y)
print "y=",y
break
yourandom(x,d,r)

Cannot understand an answer to an algorithm

I was doing this question today.
Basically, question asks for the largest 'Decent' Number having N digits where 'Decent' number is:
Only 3 and 5 as its digits.
Number of times 3 appears is divisible by 5.
Number of times 5 appears is divisible by 3.
Input Format
The 1st line will contain an integer T, the number of test cases,
followed by T lines, each line containing an integer N i.e. the number
of digits in the number
Output Format
Largest Decent number having N digits. If no such number exists, tell
Sherlock that he is wrong and print '-1'
Sample Input
4
1
3
5
11
Sample Output
-1
555
33333
55555533333
Explanation
For N=1 , there is no such number. For N=3, 555 is only possible
number. For N=5, 33333 is only possible number. For N=11 , 55555533333
and all of permutations of digits are valid numbers, among them, the
given number is the largest one.
I've solved it using normal method but saw this answer:
t = int(raw_input())
for _ in range(t):
n = int(raw_input())
c3 = 5*(2*n%3)
if c3 > n:
print -1
else:
print '5' * (n-c3) + '3'*c3
Can anyone explain the method please? Especially the line 'c3 = 5*(2*n%3)', thanks
We are looking for integer solutions of n = 5*x + 3*y where 5*x is the number of 3s and 3*y is the number of 5s. Both x and y must be >= 0 and x should be as small as possible since we can build larger numbers if we have more 5s.
Transforming this gives y = (n-5*x)/3. In order for y to be an integer n-5*x must be a multiple of 3 so we can calculate modulo 3 (I write == for is congruent modulo 3 from now on).
n-5*x == 0
n == 5*x == 2*x (because 5 == 2)
multiplying both sides by 2 gives
2*n == 4*x == x (because 4 == 1)
Since we want x small we take x = 2 * n % 3 and y = (n-5*x)/3
There is no solution if y < 0.

Matrix linear indexing

I need to traverse a rectangular grid in continuous manner. Here is an example of what I want, the number means sequence:
+ x
y 0 1 2
5 4 3
6 7 8
At each step I know the index in matrix. Is there any way to calculate the coordinates? The inverse mapping for [x + y * width] doesn't help, beacuse it creates "steps" or "jumps". Is there any solution?
Here is explanation for "steps" mentioned above:
+ x
y 0 1 2
3 4 5 //at this moment the X coordinate changes by 3, thus create step
6 7 8
y = index / width
if( y % 2 == 0 )
x = index % width
else
x = width - index % width - 1
I think that should do it. It's a single modification of the standard way of calculating with "steps" as you call them. You are only changing the way the calculation is done based upon the row.
so you need to first increase the "x" component and then decrease right - so that you get a kind of snake-behavior? You will need an if statement (or some kind of modulo - magic). Let my try the magic:
y := floor(i/columnCount)
x = (y mod 2)*(i - y*columCount) + ((y+1) mod 2)*((columnCount -1) - (i - y*columnCount))

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