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more comments for day 11

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This commit is contained in:
Bruno Raoult
2021-12-12 21:13:24 +01:00
parent b06d784563
commit 60a042951b
1 changed files with 32 additions and 21 deletions
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53
2021/day11/aoc-c.c
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@@ -24,21 +24,9 @@
static int grid[MAX_GRID][MAX_GRID]; static int grid[MAX_GRID][MAX_GRID];
static int gsize; /* real grid size */ static int gsize; /* real grid size */
static int stack[MAX_GRID * MAX_GRID]; /* flashing stack */ static int stack[MAX_GRID * MAX_GRID]; /* flashing BFS stack */
static int nstack; /* current stack size */ static int nstack; /* current stack size */
#define VALID(x, y) ((x) >= 0 && (y) >= 0 && (x) < gsize && (y) < gsize)
inline static int push(int l, int c)
{
return ((stack[nstack++] = l * gsize + c));
}
inline static int pop()
{
return nstack? stack[--nstack]: -1;
}
#ifdef DEBUG #ifdef DEBUG
static void print_grid(int (*arr)[MAX_GRID], int step) static void print_grid(int (*arr)[MAX_GRID], int step)
{ {
@@ -52,7 +40,25 @@ static void print_grid(int (*arr)[MAX_GRID], int step)
} }
#endif #endif
inline static int flash_cell_maybe(int l, int c) /* is a cell within limits ? */
#define VALID(x, y) ((x) >= 0 && (y) >= 0 && (x) < gsize && (y) < gsize)
/* push cell to BFS stack */
inline static int push(int l, int c)
{
return ((stack[nstack++] = l * gsize + c));
}
/* pop cell from BFS stack */
inline static int pop()
{
return nstack? stack[--nstack]: -1;
}
/* increase octopuss energy value, possibly flash it (= push to BFS stack)
* return 1 if flashed.
*/
inline static int inc_cell_value(int l, int c)
{ {
if (VALID(l, c) && ++grid[l][c] == 10) { if (VALID(l, c) && ++grid[l][c] == 10) {
push(l, c); push(l, c);
@@ -61,7 +67,9 @@ inline static int flash_cell_maybe(int l, int c)
return 0; return 0;
} }
/* run 1 step */ /* run 1 full step.
* return number of flashed octopuses
*/
static int do_step() static int do_step()
{ {
int vpop, flash = 0; int vpop, flash = 0;
@@ -69,13 +77,16 @@ static int do_step()
/* 1) increase all energy levels */ /* 1) increase all energy levels */
for (int l = 0; l < gsize; ++l) for (int l = 0; l < gsize; ++l)
for (int c = 0; c < gsize; ++c) for (int c = 0; c < gsize; ++c)
flash += flash_cell_maybe(l, c); flash += inc_cell_value(l, c);
/* 2) perform BFS until stack is empty */ /* 2) perform BFS until stack is empty */
while ((vpop = pop()) != -1) while ((vpop = pop()) != -1) {
for (int l = -1, pl = vpop / gsize, pc = vpop % gsize; l <= 1; ++l) int popl = vpop / gsize, popc = vpop %gsize;
for (int l = -1; l <= 1; ++l)
for (int c = -1; c <= 1; ++c) for (int c = -1; c <= 1; ++c)
flash += flash_cell_maybe(pl + l, pc + c); if (l || c) /* avoid popped cell */
flash += inc_cell_value(popl + l, popc + c);
}
/* 3) cleanup flashed cells */ /* 3) cleanup flashed cells */
for (int l = 0; l < gsize; ++l) for (int l = 0; l < gsize; ++l)
@@ -87,9 +98,9 @@ static int do_step()
static int part1() static int part1()
{ {
int flash = 0; int flash = 0, step;
for (int step = 0; step < 100; ++step) for (step = 0; step < 100; ++step)
flash += do_step(); flash += do_step();
return flash; return flash;
} }