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#include "aoc.h"
namespace aoc2017 {
static int pos(char cs[16], char c) {
for (int i = 0; i < 16; i++) {
if (cs[i] == c)
return i;
}
return 16;
}
static void spin(char cs[16], int x) {
x %= 16;
char ts[16] = {0};
memcpy(ts + x, cs, 16 - x);
memcpy(ts, cs + 16 - x, x);
memcpy(cs, ts, 16);
}
static void exchange(char cs[16], int x, int y) { std::swap(cs[x], cs[y]); }
static void partner(char cs[16], char c1, char c2) { exchange(cs, pos(cs, c1), pos(cs, c2)); }
static void get_number(const char** pp, int* d) {
const char* p = *pp;
while (*p >= '0' && *p <= '9') {
*d = *d * 10 + *p - '0';
p++;
}
*pp = p;
}
// static void print(char cs[16]) {
// for (int i = 0; i < 16; i++) {
// printf("%c", cs[i]);
// }
// printf("\n");
// }
static void dance(char cs[16], line_view file) {
const char* p0 = file.line;
const char* p1 = p0;
while (p1 < file.line + file.length) {
if (*p1 == ',' || *p1 == '\n') {
switch (*p0) {
case 's': {
int d = 0;
p0 += 1;
get_number(&p0, &d);
spin(cs, d);
break;
}
case 'x': {
int ds[2] = {0, 0};
p0 += 1;
get_number(&p0, &ds[0]);
p0 += 1;
get_number(&p0, &ds[1]);
exchange(cs, ds[0], ds[1]);
break;
}
case 'p':
partner(cs, *(p0 + 1), *(p0 + 3));
break;
default:
break;
}
p0 = p1 + 1;
}
p1++;
}
}
std::pair<int64_t, int64_t> day16(line_view file) {
const char* s = "abcdefghijklmnop";
char cs[16] = {0};
for (int i = 0; i < 16; i++) {
cs[i] = *(s + i);
}
size_t billion = 1000000000;
billion %= 60;
while (billion-- > 0) {
dance(cs, file);
// print(cs);
}
return {0, 0};
}
} // namespace aoc2017
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