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B2.4.3 · Sorting

Selection sort

Python · step by step

Selection sort

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Python implementation

The highlight marks the next line to execute. Values show the state before that line.

def selection_sort(items):    for start in range(len(items) - 1):        smallest = start        for j in range(start + 1, len(items)):            if items[j] < items[smallest]:                smallest = j        items[start], items[smallest] = items[smallest], items[start]    return items

Find the smallest remaining item, then swap it into place. The prefix before start is sorted. Comparisons take O(n²) even for sorted input. Auxiliary space is O(1).

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