diff --git a/2021/day16/README.txt b/2021/day16/README.txt index 9df8a6f..d7f3fc2 100644 --- a/2021/day16/README.txt +++ b/2021/day16/README.txt @@ -93,8 +93,6 @@ Here are a few more examples of hexadecimal-encoded transmissions: Decode the structure of your hexadecimal-encoded BITS transmission; what do you get if you add up the version numbers in all packets? Your puzzle answer was 923. - -The first half of this puzzle is complete! It provides one gold star: * --- Part Two --- Now that you have the structure of your transmission decoded, you can calculate the value of the expression it represents. @@ -123,3 +121,7 @@ For example: 9C0141080250320F1802104A08 produces 1, because 1 + 3 = 2 * 2. What do you get if you evaluate the expression represented by your hexadecimal-encoded BITS transmission? + +Your puzzle answer was 258888628940. + +Both parts of this puzzle are complete! They provide two gold stars: ** diff --git a/2021/day16/aoc-c.c b/2021/day16/aoc-c.c index 8033c5e..0629886 100644 --- a/2021/day16/aoc-c.c +++ b/2021/day16/aoc-c.c @@ -23,17 +23,17 @@ #include "bits.h" #include "list.h" -#define MAX_SUBPACKETS 1024 +#define TYPE_SUM 0 +#define TYPE_PRODUCT 1 +#define TYPE_MIN 2 +#define TYPE_MAX 3 +#define TYPE_VALUE 4 +#define TYPE_GREATER 5 +#define TYPE_LESS 6 +#define TYPE_EQUAL 7 -#define TYPE_VAL 4 - -struct packet { - u8 version; - u8 type; - u64 value; -}; - -static u64 totversions; +#define MAX_STACK 128 /* max stack for operators input */ +static u64 totversions; /* sum of versions */ static u64 bitval(char *p, int length) { @@ -41,9 +41,7 @@ static u64 bitval(char *p, int length) for (; length; length--, p++) { u8 b = *p -'0'; val += b << (length - 1); - //printf("%c -> %d, %lu\n", *p, b, val); } - //printf("%lu\n", val); return val; } @@ -54,63 +52,89 @@ static u64 decode_value(char *bits, char **end) for (u64 tmp = 16; tmp & 16; bits += 5) { tmp = bitval(bits, 5); val = val << 4 | (tmp & 15); - //printf("bits =%5s tmp=%lu xor=%lu val=%lu\n", bits, tmp, tmp & 15, val); } *end = bits; return val; } -int weight[] = { - ['B'] = 0, ['C'] = 1, ['F'] = 2, - ['H'] = 3, ['K'] = 4, ['N'] = 5, ['O'] = 6, - ['P'] = 7, ['S'] = 8, ['V'] = 9 -}; - -static struct packet decode(char *start, char **end) +static s64 decode(char *start, char **end) { - struct packet packet; - char *cur; - s64 count; + u8 type; + s64 count, result = 0; + s64 stack[MAX_STACK]; + int nstack = 0; - //printf("decode(%.4s...)\n", start); - packet.version = bitval(start, 3); - totversions += packet.version; - packet.type = bitval(start + 3, 3); - log_f(3, "[%.6s...] version=%d type=%d\n", start, packet.version, packet.type); - cur = start + 6; - switch (packet.type) { - case TYPE_VAL: - packet.value = decode_value(cur, end); - printf("val = %lu len=%lu\n", packet.value, *end - cur); + totversions += bitval(start, 3); /* decode version & type */ + type = bitval(start + 3, 3); + start += 6; + + if (type == TYPE_VALUE) + return decode_value(start, end); + + switch (*start++) { + case '0': + count = bitval(start, 15); + start += 15; + *end = start; + log(3, "nbits = %lu\n", count); + while ((*end - start) < count) { + stack[nstack++] = decode(*end, end); + //log(3, " end - start = %lu\n", *end - start); + log(3, " stack %d = %ld\n", nstack - 1, stack[nstack - 1]); + } break; - default: - switch (*cur++) { - case '0': - count = bitval(cur, 15); - cur += 15; - *end = cur; - printf("nbits = %lu\n", count); - while ((*end - cur) < count) { - decode(*end, end); - printf(" end - cur = %lu\n", *end - cur); - } - break; - case '1': - count = bitval(cur, 11); - cur += 11; - *end = cur; - printf("npackets = %ld\n", count); - while (count--) { - decode(*end, end); - printf(" count = %ld\n", count); - } - + case '1': + count = bitval(start, 11); + start += 11; + *end = start; + log(3, "npackets = %ld\n", count); + while (count--) { + stack[nstack++] = decode(*end, end); + log(3, " stack %d = %ld\n", nstack - 1, stack[nstack - 1]); } } + switch (type) { + case TYPE_SUM: + log(3, "OP=sum\n"); + while (--nstack > -1) + result += stack[nstack]; + break; + case TYPE_PRODUCT: + result = 1; /* forgot this one ;-) */ + log(3, "OP=mult\n"); + while (--nstack > -1) + result *= stack[nstack]; + break; + case TYPE_MIN: + result = INT64_MAX; + log(3, "OP=min\n"); + while (--nstack > -1) + if (stack[nstack] < result) + result = stack[nstack]; + break; + case TYPE_MAX: + log(3, "OP=max\n"); + while (--nstack > -1) + if (stack[nstack] > result) + result = stack[nstack]; + break; + case TYPE_GREATER: + log(3, "OP=gt\n"); + result = stack[0] > stack[1]? 1: 0; + break; + case TYPE_LESS: + log(3, "OP=le\n"); + result = stack[0] < stack[1]? 1: 0; + break; + case TYPE_EQUAL: + log(3, "OP=eq\n"); + result = stack[0] == stack[1]? 1: 0; + } + //log_f(3, "bin=[%s] version=%d type=%d\n", bits, version, type); - //log_f(3, "[%s] version=%d type=%d\n", start, packet.version, packet.type); - return packet; + //log_f(3, "[%s] version=%d type=%d\n", start, version, type); + return result; } /* read BITS data @@ -139,24 +163,6 @@ free: return bits; } -/* -static u32 doit() -{ - return 1; -} - - -static u32 part1() -{ - return doit(); -} - -static u32 part2() -{ - return doit(); -} -*/ - static int usage(char *prg) { fprintf(stderr, "Usage: %s [-d debug_level] [-p part]\n", prg); @@ -187,8 +193,8 @@ int main(int ac, char **av) buf = read_input(); - decode(buf, &end); - printf("END: end=%lu sum_versions=%lu\n", end - buf, totversions); + s64 result = decode(buf, &end); + printf("END: end=%lu sum_versions=%lu result=%ld\n", end - buf, totversions, result); //printf("%s : res=%u\n", *av, part == 1? part1(): part2()); exit (0); }