Efficient Algorithm for String Concatenation with Overlap

Question

We need to combine 3 columns in a database by concatenation. However, the 3 columns may contain overlapping parts and the parts should not be duplicated. For example,

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Answer 1

Here's a solution in Python. It should be faster just by not needing to build substrings in memory all the time. The work is done in the _concat function, which concatenates two strings. The concat function is a helper that concatenates any number of strings.

def concat(*args):
    result = ''
    for arg in args:
        result = _concat(result, arg)
    return result

def _concat(a, b):
    la = len(a)
    lb = len(b)
    for i in range(la):
        j = i
        k = 0
        while j < la and k < lb and a[j] == b[k]:
            j += 1
            k += 1
        if j == la:
            n = k
            break
    else:
        n = 0
    return a + b[n:]

if __name__ == '__main__':
    assert concat('a', 'b', 'c') == 'abc'
    assert concat('abcde', 'defgh', 'ghlmn') == 'abcdefghlmn'
    assert concat('abcdede', 'dedefgh', '') == 'abcdedefgh'
    assert concat('abcde', 'd', 'ghlmn') == 'abcdedghlmn'
    assert concat('abcdef', '', 'defghl') == 'abcdefghl'