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#include "aoc.h"
#include <string.h>
#include <string>
#include <vector>
namespace aoc2019 {
bool smaller(const char* s1, const char* s2) { return std::atoi(s1) < std::atoi(s2); }
bool two_identical(const char* s) {
const char* n = s + strlen(s);
while (s < n - 1) {
if (*s == *(s + 1)) {
return true;
}
s++;
}
return false;
}
bool two_identical_plus(const char* s) {
auto is_right = [s](int i, int j) -> bool {
bool b1 = s[i] == s[j];
bool b2 = i > 0 ? s[i] != s[i - 1] : true;
bool b3 = j < 5 ? s[j] != s[j + 1] : true;
return b1 && b2 && b3;
};
for (int i = 0; i < 5; i++) {
if (is_right(i, i + 1)) {
return true;
}
}
return false;
}
typedef bool (*identical_f)(const char*);
void next(size_t i, size_t j, char p[], const char* low, const char* high, int* c1, int* c2) {
static char digits[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'};
if (i == strlen(high)) {
if (smaller(p, high) && smaller(low, p)) {
*c1 += int(two_identical(p));
*c2 += int(two_identical_plus(p));
}
} else {
for (size_t x = j; x < ARRAY_SIZE(digits); x++) {
p[i] = digits[x];
next(i + 1, x, p, low, high, c1, c2);
}
}
}
std::pair<int, int> day4(const char* low, const char* high) {
char pass[7] = {0};
int c1{0};
int c2{0};
next(0, 0, pass, low, high, &c1, &c2);
return {c1, c2};
}
} // namespace aoc2019
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