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import std.stdio, std.ascii, std.algorithm, std.array, std.range;
alias Block = char[2];
bool canMakeWord(immutable Block[] blocks, in string word) pure nothrow
in {
assert(blocks.all!(w => w[].all!isAlpha));
assert(word.all!isAlpha);
} body {
bool inner(size_t[] indexes, in string w) pure nothrow {
if (w.empty)
return true;
immutable c = w[0].toUpper;
foreach (ref idx; indexes) {
if (blocks[idx][0].toUpper != c &&
blocks[idx][1].toUpper != c)
continue;
indexes[0].swap(idx);
if (inner(indexes[1 .. $], w[1 .. $]))
return true;
indexes[0].swap(idx);
}
return false;
}
return inner(blocks.length.iota.array, word);
}
void main() {
enum Block[] blocks = "BO XK DQ CP NA GT RE TG QD FS
JW HU VI AN OB ER FS LY PC ZM".split;
foreach (w; "" ~ "A BARK BoOK TrEAT COmMoN SQUAD conFUsE".split)
writefln(`"%s" %s`, w, blocks.canMakeWord(w));
// Extra test.
immutable Block[] blocks2 = ["AB", "AB", "AC", "AC"];
immutable word = "abba";
writefln(`"%s" %s`, word, blocks2.canMakeWord(word));
}
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