Rearranging numbers in a string

Question

Rearrange Numbers in String

Given a string, write a program to re-arrange all the numbers appearing in the string in decreasing order. Note: There will not be any negative numbers or numbers with decimal part.

Input

The input will be a single line containing a string.

Output

The output should be a single line containing the modified string with all the numbers in string re-ordered in decreasing order.

Explanation:

For example, if the given string is "I am 5 years and 11 months old", the numbers are 5, 11. Your code should print the sentence after re-ordering the numbers as "I am 11 years and 5 months old".

#Sample Input:
I am 5 years and 11 months old

#Sample Output:
I am 11 years and 5 months old

#Sample input:
I am 28 years 9 months 11 weeks and 55 days old

#Sample output:
I am 55 years 28 months 11 weeks and 9 days old

My approach:

def RearrangeNumbers(source):
    tmp0 = list(source)
    tmp1 = [c if c.isdigit() else ' ' for. 
             c in tmp0 ]
    tmp2 = "".join(tmp1)
    tmp3 = tmp2.split()
    numbers = []
    for w in tmp3:
        numbers.append(int(w))
    if len(numbers) < 2:
        return source
    numbers.sort(reverse=True)
    result_string = ''
    i = 0
    while i < len(source): 
        c = source[i]
        if not c.isdigit():
            result_string += c
        else:
            result_string += str(numbers[0])
            numbers = numbers[1:]
            i+=1
        i+=1
    return result_string

print(RearrangeNumbers(input()))

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Output:

I am 55 years 28months 11 weeks and 9 days old

But there should be space between 28months

Answer 1

You do a lot of string manipulation on a character by character basis in your code. Finding numbers digit-wise is a complicated way to do what you must do. Your lost space is caused by your approach:

Hint: check the length's of your numbers in your text - you may not always replace a 1-digit number by another 1-digit number - sometimes you would need to replace a 1-digit number by a 3 digit number:

"Try 1 or 423 or 849 things."

and in that case your "char-by-char" replacing will get wonky and you loose the space.

Essentially you replace "2 " by a 2-digit number (or "12 " by a 3-digit one etc. killing the space).

---

It would be better to

• detect all numbers
• sort detected numbers by their integer value descending
• replace all detected numbers in your text with format-placeholder '{}'
• use string.formt() to substitute numbers in correct order

like so:

def sortNumbers(text):
    # replace all non-digit characters by space, split result
    numbers = ''.join(t if t.isdigit() else ' ' for t in text).split()

    # order descending by integer value
    numbers.sort(key=lambda x:-int(x))  

    # replace all found numbers - do not mess with the original string with 
    # respect to splitting, spaces or anything else - multiple spaces
    # might get reduced to 1 space if you "split()" it.
    for n in numbers:
        text = text.replace(n, "{}")

    return text.format(*numbers)  # put the sorted numbers back into the string

for text in ["I am 5 years and 11 months old",
            "I am 28 years 9 months 11 weeks and 55 days old",
            "What is 5 less then 45?",
            "At 49th Street it is 500.", "It is $23 and 45."]:

    print(sortNumbers(text))

Output:

I am 11 years and 5 months old
I am 55 years 28 months 11 weeks and 9 days old
What is 45 less then 5?
At 500th Street it is 49.
It is $45 and 23.