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| author | June McEnroe <june@causal.agency> | 2020-12-15 02:02:00 -0500 |
|---|---|---|
| committer | June McEnroe <june@causal.agency> | 2020-12-15 02:02:00 -0500 |
| commit | 519aa25c89bc5f372b9ca6727e8026fbba319e4f (patch) | |
| tree | 643e212d5ac90b7ad18426ce13efa749651e0780 | |
| parent | Solve day 15 part 2 (diff) | |
| download | aoc-519aa25c89bc5f372b9ca6727e8026fbba319e4f.tar.gz aoc-519aa25c89bc5f372b9ca6727e8026fbba319e4f.zip | |
Update day 14 part 2 with the clever way
| -rw-r--r-- | 2020/day14.c | 14 |
1 files changed, 3 insertions, 11 deletions
diff --git a/2020/day14.c b/2020/day14.c index 07bab22..78f1885 100644 --- a/2020/day14.c +++ b/2020/day14.c @@ -38,18 +38,10 @@ int main(void) { writes[len++] = (struct Write) { addr, (val & mask) | bits }; addr |= bits; addr &= ~mask; - ul count = 1UL << __builtin_popcountl(mask); - for (ul i = 0; i < count; ++i) { - ul a = addr; - ul w = i; - for (int j = 0; j < 36; ++j) { - if (mask & (1UL << j)) { - a |= (w & 1) << j; - w >>= 1; - } - } - writes2[len2++] = (struct Write) { a, val }; + for (ul m = mask; m; m = (m - 1) & mask) { + writes2[len2++] = (struct Write) { addr | m, val }; } + writes2[len2++] = (struct Write) { addr, val }; } } mergesort(writes, len, sizeof(writes[0]), compar); |