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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define arrlen(x) (sizeof(x)/sizeof((x)[0]))
struct rock {
unsigned char s[4];
};
struct rock const rocks[] = {
{ { 0x1e, 0, 0, 0 } }, // Horizontal line
{ { 0x08, 0x1c, 0x08, 0 } }, // Cross
{ { 0x1c, 0x04, 0x04, 0 } }, // Elbow
{ { 0x10, 0x10, 0x10, 0x10 } }, // Line piece
{ { 0x18, 0x18, 0, 0 } }, // Block
};
#if 0
void
chamber_dump(unsigned char * chamber, int chamberheight, struct rock * rock, int rockheight)
{
int i;
for (i = chamberheight - 1; i >= 0; --i) {
unsigned char c;
fputc('|', stderr);
for (c = 0x40; c != 0; c >>= 1) {
if (rock && i >= rockheight
&& i < rockheight + arrlen(rock->s)
&& (rock->s[i - rockheight] & c))
fputc('@', stderr);
else if (chamber && (chamber[i] & c))
fputc('#', stderr);
else
fputc('.', stderr);
}
fputc('|', stderr);
fputc('\n', stderr);
}
fprintf(stderr, "+-------+\n");
}
#endif
int
main()
{
size_t jetsize = 0;
char * jets = NULL;
unsigned char * chamber = NULL;
int chamberheight = 0, top = 0;
int movement, rocknum, rockheight;
struct rock rock;
int i;
// Read jets.
while (1) {
void * p;
size_t s;
if ((p = realloc(jets, jetsize + BUFSIZ)) == NULL) {
fprintf(stderr, "jets: bad realloc (%zu)\n", jetsize + BUFSIZ);
free(jets);
return -1;
}
jets = p;
if ((s = fread(jets + jetsize, 1, BUFSIZ, stdin)) == 0)
break;
jetsize += s;
}
// Remove any characters that are not '<' or '>' (e.g. newlines)
for (i = 0; i < jetsize; ++i) {
while (i < jetsize && jets[i] != '<' && jets[i] != '>') {
memmove(jets + i, jets + i + 1, jetsize - (i + 1));
--jetsize;
}
}
// Place first rock, and start movement
rocknum = 0;
rock = rocks[rocknum];
rockheight = 3;
for (movement = 0; rocknum < 2022; ++movement) {
int jet;
if (top > chamberheight - 10) {
void * p;
if ((p = realloc(chamber, chamberheight + BUFSIZ)) == NULL) {
fprintf(stderr, "Bad realloc(%d)\n", chamberheight + BUFSIZ);
free(chamber);
return -1;
}
chamber = p;
memset(chamber + chamberheight, 0, BUFSIZ);
chamberheight += BUFSIZ;
}
jet = jets[movement % jetsize];
// Check if jet can push rock.
for (i = 0; i < arrlen(rock.s); ++i) {
// Check left wall collision
if (jet == '<' && (rock.s[i] & 0x40) != 0)
jet = 0;
// Check right wall collision
if (jet == '>' && (rock.s[i] & 0x01) != 0)
jet = 0;
// Check moving left into existing rocks.
if (jet == '<' && ((rock.s[i] << 1) & chamber[rockheight + i]) != 0)
jet = 0;
// Check moving right into existing rocks
if (jet == '>' && ((rock.s[i] >> 1) & chamber[rockheight + i]) != 0)
jet = 0;
}
// If jet can push rock, do so.
if (jet == '<')
for (i = 0; jet && i < arrlen(rock.s); ++i)
rock.s[i] <<= 1;
if (jet == '>')
for (i = 0; jet && i < arrlen(rock.s); ++i)
rock.s[i] >>= 1;
// Check if rock can fall.
for (i = 0; rockheight > 0 && i < arrlen(rock.s); ++i)
if ((rock.s[i] & chamber[rockheight - 1 + i]) != 0)
break;
if (i < arrlen(rock.s)) {
// Rock cannot fall. Place rock.
for (i = 0; i < arrlen(rock.s) && rock.s[i] != 0; ++i) {
chamber[rockheight + i] |= rock.s[i];
if (rockheight + i > top)
top = rockheight + i;
}
// Pick next rock.
rock = rocks[++rocknum % arrlen(rocks)];
rockheight = top + 4;
#if 0
chamber_dump(chamber, top + 7, &rock, rockheight);
#endif
}
else {
// Rock can fall, so reduce its height by 1
--rockheight;
}
}
printf("Height of rocks in chamber: %d\n", top + 1);
free(chamber);
free(jets);
return 0;
}
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