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| -rw-r--r-- | challenge-030/paulo-custodio/c/ch-1.c | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/challenge-030/paulo-custodio/c/ch-1.c b/challenge-030/paulo-custodio/c/ch-1.c new file mode 100644 index 0000000000..35e3e832df --- /dev/null +++ b/challenge-030/paulo-custodio/c/ch-1.c @@ -0,0 +1,45 @@ +/* +Challenge 030 + +Task #1 +Write a script to list dates for Sunday Christmas between 2019 and 2100. For +example, 25 Dec 2022 is Sunday. +*/ + +#include <assert.h> +#include <stdio.h> +#include <stdbool.h> + +enum { Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday }; + +int day_of_week(int y, int m, int d) { + return (d += m < 3 ? y-- : y - 2, 23*m/9 + d + 4 + y/4- y/100 + y/400)%7; +} + +bool is_leap_year(int y) { + return y%400==0 ? true : y%100==0 ? false : y%4==0 ? true : false; +} + +int days_of_month(int y, int m) { + switch (m) { + case 1: case 3: case 5: case 7: case 8: case 10: case 12: return 31; + case 4: case 6: case 9: case 11: return 30; + case 2: return is_leap_year(y) ? 29 : 28; + default: assert(0); + } +} + +void print_sunday_christmas(int start_year, int end_year) { + const char* sep = ""; + for (int y = start_year; y <= end_year; y++) { + if (day_of_week(y, 12, 25) == Sunday) { + printf("%s%04d", sep, y); + sep = ", "; + } + } + printf("\n"); +} + +int main() { + print_sunday_christmas(2019, 2100); +} |