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author | June McEnroe <june@causal.agency> | 2021-12-08 16:13:15 -0500 |
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committer | June McEnroe <june@causal.agency> | 2021-12-08 16:19:10 -0500 |
commit | e9f215d5af190f33c2f29d145b4b28785ba7400b (patch) | |
tree | 04f8314161293af49fd8664059e90de46cda4585 /2021/day08-2.c | |
parent | Solve day 8 part 1 (diff) | |
download | aoc-e9f215d5af190f33c2f29d145b4b28785ba7400b.tar.gz aoc-e9f215d5af190f33c2f29d145b4b28785ba7400b.zip |
Solve day 8 part 2
That took me way too long from dumb mistakes.
Diffstat (limited to '')
-rw-r--r-- | 2021/day08-2.c | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/2021/day08-2.c b/2021/day08-2.c new file mode 100644 index 0000000..9aa67c5 --- /dev/null +++ b/2021/day08-2.c @@ -0,0 +1,84 @@ +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +static int segDigit(int seg) { + switch (seg) { + case 0x77: return 0; + case 0x12: return 1; + case 0x5D: return 2; + case 0x5B: return 3; + case 0x3A: return 4; + case 0x6B: return 5; + case 0x6F: return 6; + case 0x52: return 7; + case 0x7F: return 8; + case 0x7B: return 9; + default: return -1; + } +} +struct Map { + int m[7]; +}; +static int mapDigit(struct Map map, int seg) { + int x = 0; + for (int i = 0; i < 7; ++i) { + if (seg & (1 << map.m[i])) x |= 1 << i; + } + return segDigit(x); +} +static int mapValid(struct Map map, int segs[]) { + int got[10] = {0}; + for (int i = 0; i < 10; ++i) { + int digit = mapDigit(map, segs[i]); + if (digit < 0) return 0; + got[digit]++; + } + for (int i = 0; i < 10; ++i) { + if (got[i] != 1) return 0; + } + return 1; +} +static void swap(int *a, int *b) { + int x = *a; + *a = *b; + *b = x; +} +static int mapPermute(struct Map *map, int i, int segs[]) { + for (int j = i; j < 7; ++j) { + swap(&map->m[i], &map->m[j]); + if (mapPermute(map, i+1, segs)) return 1; + swap(&map->m[i], &map->m[j]); + } + return mapValid(*map, segs); +} +static int segParse(const char *s) { + int x = 0; + for (; *s; ++s) { + x |= 1 << (*s - 'a'); + } + return x; +} +int main(void) { + int sum = 0; + size_t cap = 0; + char *buf = NULL; + while (0 < getline(&buf, &cap, stdin)) { + int segs[10], outs[4]; + char *ptr = buf; + for (int i = 0; i < 10; ++i) { + segs[i] = segParse(strsep(&ptr, " ")); + } + strsep(&ptr, " "); + for (int i = 0; i < 4; ++i) { + outs[i] = segParse(strsep(&ptr, " \n")); + } + struct Map map = { { 0, 1, 2, 3, 4, 5, 6 } }; + int valid = mapPermute(&map, 0, segs); + if (!valid) printf("oops!\n"); + for (int i = 0; i < 4; ++i) { + outs[i] = mapDigit(map, outs[i]); + } + sum += outs[0]*1000 + outs[1]*100 + outs[2]*10 + outs[3]; + } + printf("%d\n", sum); +} |