http://okajima.air-nifty.com/b/2010/01/post-abc6.html 適当に sed で解いてみた。サイズ決め打ちで書いたら割と簡単だった… H ${ x # initialize seen positions h x s/.\(.\{25\}\).S.\(.\{25\}\)./*\1***\2*/ x # initialize initial state of the queue s/S /SN/ /N/{H;s/N/ /} s/ S/NS/ /N/{H;s/N/ /} s/\(S.\{26\}\) /\1N/ /N/{H;s/N/ /} s/ \(.\{26\}S\)/N\1/ /N/{H;s/N/ /} # add the marker x s/^\n/-&/ s/\n\n/\n=\n/ x : # load the queue g s/\n\n