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Remove uneeded branches in update()

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Now that the value and possible values are independent, it doesn't
matter if we clobber the possible values of a cell that's been
determined.
This commit is contained in:
Camden Dixie O'Brien 2022-11-24 01:37:40 +00:00
parent 1a84d900f2
commit 7c6efa125e
1 changed files with 6 additions and 15 deletions
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21
sud.c
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@ -54,30 +54,21 @@ enum update_res update(struct sudoku *sud, unsigned r, unsigned c, unsigned val)
unsigned tr, tc;
const uint16_t clearmask = ~(1 << val);
/* Update possible values of cells in same column. */
for (tr = 0; tr < NDIGITS; ++tr) {
if (tr == r || DET(sud->cells[tr][c]))
continue;
sud->cells[tr][c] &= clearmask;
}
/* Update possible values of cells in same row. */
for (tc = 0; tc < NDIGITS; ++tc) {
if (tc == c || DET(sud->cells[r][tc]))
continue;
for (tc = 0; tc < NDIGITS; ++tc)
sud->cells[r][tc] &= clearmask;
}
/* Update possible values of cells in same column. */
for (tr = 0; tr < NDIGITS; ++tr)
sud->cells[tr][c] &= clearmask;
/* Update possible values of cells in same segment. */
const unsigned segr0 = SEGLEN * (r / SEGLEN);
const unsigned segc0 = SEGLEN * (c / SEGLEN);
for (tr = segr0; tr < segr0 + SEGLEN; ++tr) {
for (tc = segc0; tc < segc0 + SEGLEN; ++tc) {
if ((tr == r && tc == c) || DET(sud->cells[tr][tc]))
continue;
for (tc = segc0; tc < segc0 + SEGLEN; ++tc)
sud->cells[tr][tc] &= clearmask;
}
}
/* Set the cell's value. */
sud->cells[r][c] |= DETMASK;