Advanced · Sorting algorithms · 174 of 264
Sort by digit sum
Sort positive numbers by the sum of their digits; numbers with the same digit sum by their value.
Input: positive whole numbers on one line. Output: the sorted numbers.
Examples
Input
19 5 23 100
Output
100 5 23 19
Input
11 2 20
Output
2 11 20
Input
7
Output
7
One more test checks other inputs when you press Check.
Stuck? The idea behind sorting algorithms
Bubble sort swaps neighbours that are in the wrong order, pass after pass. Insertion sort takes each item in turn and slides it back into place among those before it. Merge sort splits the list, sorts each half and merges them.
These exercises ask for the steps, not just the result: write the algorithm yourself rather than calling sorted().
a = [5, 1, 4, 2]
for end in range(len(a) - 1, 0, -1):
for i in range(end):
if a[i] > a[i + 1]:
a[i], a[i + 1] = a[i + 1], a[i]
print(a)Watch for: Off-by-one: comparing a[i] with a[i + 1] means i must stop one before the end.