Popping Pairs

Easy

In a game, a row of balls lies on a track, each labeled with a lowercase English letter; the row is written as the string text. When two neighbouring balls are the same, they pop and the rest close the gap, which may bring new equal neighbours together. Pairs keep popping until no equal neighbours remain. Return the string of balls that are left. It can be shown that the result does not depend on the order in which pairs pop.

Example 1

text="kayyak" → ''

Remove yy to get kaak, then aa to get kk, then kk leaves an empty string.

Example 2

text="abccbd" → 'ad'

Removing cc brings the two bs together; they go too, leaving ad.

Example 3

text="xyz" → 'xyz'

Constraints

1 ≤ len(text) ≤ 10⁵
text consists of lowercase English letters

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Topics

Stack String

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Input

text="kayyak"

Expected

''

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