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when rule 4 is violated, skip to next possible number

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This commit is contained in:
Bruno Raoult
2022-09-18 13:23:53 +02:00
parent a461bf2842
commit f7336d6814
2 changed files with 41 additions and 14 deletions
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8
2019/RESULTS.txt
View File

@@ -46,10 +46,10 @@ aoc-c : res=9238
+++++++++++++++++ part 1 +++++++++++++++++ part 1
aoc-c : res=2090 aoc-c : res=2090
time: 0:00.01 real, 0.01 user, 0.00 sys time: 0:00.00 real, 0.00 user, 0.00 sys
context-switch: 2+1, page-faults: 0+88 context-switch: 0+1, page-faults: 0+90
+++++++++++++++++ part 2 +++++++++++++++++ part 2
aoc-c : res=1419 aoc-c : res=1419
time: 0:00.01 real, 0.00 user, 0.00 sys time: 0:00.00 real, 0.00 user, 0.00 sys
context-switch: 3+1, page-faults: 0+91 context-switch: 0+1, page-faults: 0+89

47
2019/day04/aoc-c.c
View File

@@ -18,17 +18,45 @@
#include <getopt.h> #include <getopt.h>
#include "debug.h" #include "debug.h"
#include "likely.h"
static int is_valid(int number, int part) /**
* next_number() - finds next suitable number after a faulty right digit
* @number: the number
* @faulty: the faulty digit position (1, 10, 100, etc...)
* @left: the left digit of faulty one
*
* This function is called when rule 4 is violated:
* "Going from left to right, the digits never decrease."
* Example: 453456
* ^
* Here we will replace the faulty digit and next ones with its left digit
* value (5 here). Returned number will be 455555.
* This function allowed to save 546,495/548,022 calls to is_valid(), which
* is 99.7%.
*/
static int next_number(int number, int faulty, int left)
{ {
int valid = 0, dups[10] = { 0 }; int next = number - number % (faulty * 10);
int digit, dec;
for (digit = number % 10; number > 10; digit = dec) { for (; faulty; faulty /= 10)
next += left * faulty;
return next;
}
static int is_valid(int number, int part, int *next)
{
int valid = 0, dups[10] = { 0 }, work = number;
int digit, dec = number + 1, faulty = 1;
*next = number + 1;
for (digit = number % 10; number > 10; digit = dec, faulty *= 10) {
number /= 10; number /= 10;
dec = number % 10; dec = number % 10;
if (dec > digit) if (dec > digit) {
*next = next_number(work, faulty, dec);
return 0; return 0;
}
if (dec == digit) { if (dec == digit) {
valid = 1; valid = 1;
dups[digit] += 2; dups[digit] += 2;
@@ -44,13 +72,12 @@ static int is_valid(int number, int part)
static int doit(int *nums, int part) static int doit(int *nums, int part)
{ {
int res = 0; int res = 0, next = 0;
/* There is surely a way to avoid 99% of useless calls to is_valid. for (int i = nums[0]; i < nums[1]; i = next) {
*/ if (unlikely(is_valid(i, part, &next)))
for (int i = nums[0]; i < nums[1]; ++i)
if (is_valid(i, part))
res++; res++;
}
return res; return res;
} }