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2023/day3: add part2 C solution

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This commit is contained in:
Zack Buhman 2024-04-12 14:12:07 +08:00
parent f47dbb6691
commit 959989750e
2 changed files with 80 additions and 27 deletions
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1
.gitignore vendored
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@ -3,3 +3,4 @@
*.bin
*.d
*.map
*.out

106
2023/day3/part1.c → 2023/day3/_solution.c
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@ -66,15 +66,9 @@ uint32_t ix_from_xy(uint8_t const * const start,
return (stride * y + x);
}
static const uint8_t symbols[] = {'@', '&', '=', '/', '-', '+', '%', '*', '$', '#'};
bool is_symbol(uint8_t const * const start,
uint32_t const stride,
uint32_t const x,
uint32_t const y)
bool is_symbol(uint8_t const c)
{
uint32_t const ix = ix_from_xy(start, stride, x, y);
uint8_t const c = start[ix];
static uint8_t const symbols[] = {'@', '&', '=', '/', '-', '+', '%', '*', '$', '#'};
for (uint32_t i = 0; i < (sizeof (symbols)) / (sizeof (*symbols)); i++) {
if (c == symbols[i]) {
@ -84,38 +78,90 @@ bool is_symbol(uint8_t const * const start,
return false;
}
bool is_gear(uint8_t const c)
{
return c == '*';
}
struct adjacency {
uint32_t ix;
int32_t count;
int32_t neighbors[4];
};
int32_t last_gear = 0;
struct adjacency gears[512] = {0};
void update_gear_adjacencies(uint32_t gear_ix, uint32_t num)
{
for (int i = 0; i < (sizeof (gears)) / (sizeof (*gears)); i++) {
if (i >= last_gear) {
gears[last_gear++].ix = gear_ix;
}
if (gears[i].ix == gear_ix) {
if (gears[i].count < 4) {
gears[i].neighbors[gears[i].count++] = num;
}
break;
}
}
}
void adjacency_check(uint8_t const * const start,
uint32_t const stride,
int32_t const max_x,
int32_t const max_y,
int32_t const x,
int32_t const y,
uint32_t const num,
bool * neighbor)
{
if (xy_in_bounds(max_x, max_y, x, y)) {
uint32_t const ix = ix_from_xy(start, stride, x, y);
uint8_t const c = start[ix];
if (is_symbol(c))
*neighbor = true;
if (is_gear(c))
update_gear_adjacencies(ix, num);
}
}
bool has_adjacent_symbol(uint8_t const * const start,
uint32_t const stride,
int32_t const max_x,
int32_t const max_y,
int32_t const x,
int32_t const y,
int32_t const digits)
uint32_t const num,
int32_t const digits
)
{
bool neighbor = false;
/* check top/bottom/diagonals */
for (int32_t xi = x - 1; xi <= x + digits; xi++) {
if (xy_in_bounds(max_x, max_y, xi, y - 1)) {
if (is_symbol(start, stride, xi, y - 1))
return true;
}
if (xy_in_bounds(max_x, max_y, xi, y + 1)) {
if (is_symbol(start, stride, xi, y + 1))
return true;
}
adjacency_check(start, stride, max_x, max_y, xi, y + 1, num, &neighbor);
adjacency_check(start, stride, max_x, max_y, xi, y - 1, num, &neighbor);
}
/* check left/right side */
if (xy_in_bounds(max_x, max_y, x + digits, y)) {
if (is_symbol(start, stride, x + digits, y))
return true;
}
adjacency_check(start, stride, max_x, max_y, x + digits, y, num, &neighbor);
adjacency_check(start, stride, max_x, max_y, x - 1 , y, num, &neighbor);
if (xy_in_bounds(max_x, max_y, x - 1, y)) {
if (is_symbol(start, stride, x - 1, y))
return true;
}
return neighbor;
}
return false;
uint64_t part2_mac(void)
{
uint64_t mac = 0;
for (int i = 0; i < last_gear; i++) {
if (gears[i].count == 2) {
mac += (uint64_t)gears[i].neighbors[0] * (uint64_t)gears[i].neighbors[1];
}
}
return mac;
}
void solve(uint8_t const * const start,
@ -146,12 +192,18 @@ void solve(uint8_t const * const start,
max_y,
x,
y,
(int32_t)digits);
num,
(int32_t)digits
);
if (has)
sum += num;
}
printf("part1 sum: %d\n", sum);
printf("part2:\n");
printf(" gears : %d\n", last_gear);
printf(" answer: %ld\n", part2_mac());
}
int main(void)