Update answer_26.cpp#30

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jamery-huang wants to merge 4 commits intogzr2017:masterfrom

jamery-huang:master

Commits on May 15, 2020

Update answer_26.cpp
jamery-huang
authored

Commits on Dec 31, 2020

Update answer_6.cpp
jamery-huang
authored

Commits on Sep 16, 2021

Need some protections.
jamery-huang
committed

Commits on Sep 18, 2021

Consider grey level 255.
jamery-huang
committed