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day 3 part 2 (C)

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Bruno Raoult
2021-12-04 16:04:51 +01:00
parent cbe3616422
commit 401b567e20
3 changed files with 108 additions and 20 deletions
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96
2021/day03/aoc-c.c
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@@ -56,15 +56,90 @@ static int ex1()
static int ex2()
{
/* idea : Given 3 bits input
* 101
* 010
* 110
*
* we create an ushort array of size 2⁴ initialized at 2⁴
*
*/
return 1;
u32 length, size, *values, min, max, oxygen, co2;
u32 zero, one, lastone, lastzero, bit;
char buffer[80];
u64 val;
/* get length of binary number */
scanf("%s", buffer);
length = strlen(buffer);
size = 1 << length;
values = calloc(size, sizeof(*values));
do {
val = strtoul(buffer, NULL, 2);
values[val] = val;
} while (scanf("%s", buffer) != EOF);
min = 0;
max = size;
bit = size >> 1;
while (1) {
zero = 0;
one = 0;
for (u32 i = min; i < max; ++i) {
if (values[i]) {
if (values[i] & bit) {
one++;
lastone = i;
} else {
zero++;
lastzero = i;
}
}
}
if (one >= zero) {
if (one == 1) {
oxygen = lastone;
break;
}
min = (max + min) / 2;
} else {
if (zero == 1) {
oxygen = lastzero;
break;
}
max = (max + min) / 2;
}
bit >>= 1;
}
min = 0;
max = size;
bit = size >> 1;
while (1) {
zero = 0;
one = 0;
for (u32 i = min; i < max; ++i) {
if (values[i]) {
if (values[i] & bit) {
one++;
lastone = i;
} else {
zero++;
lastzero = i;
}
}
}
if (zero <= one) {
if (zero == 1) {
co2 = lastzero;
break;
}
max = (max + min) / 2;
} else {
if (one == 1) {
co2 = lastone;
break;
}
min = (max + min) / 2;
}
bit >>= 1;
}
free(values);
return oxygen * co2;
}
static int usage(char *prg)
@@ -97,8 +172,7 @@ int main(int ac, char **av)
if (exercise == 1) {
res = ex1();
printf ("%s : res=%d\n", *av, res);
}
if (exercise == 2) {
} else {
res = ex2();
printf ("%s : res=%d\n", *av, res);
}