shailpatels.me
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day 2, part 1
+47
2/main.c
+47
2/main.c
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#include <assert.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdbool.h>
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bool is_invalid_id(const long long num) {
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char str[32];
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sprintf(str, "%lld", num);
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int len = strlen(str);
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if (len % 2 != 0)
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return false;
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const int half = len / 2;
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for (int i = 0; i < half; i++)
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if (str[i] != str[i + half]) return false;
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return true;
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}
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int main(int argc, char **argv) {
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assert(argc == 2);
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FILE *file = fopen(argv[1], "r");
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assert(file != NULL);
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char *line = NULL;
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size_t len = 0;
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getline(&line, &len, file);
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fclose(file);
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long long total = 0;
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char *token = strtok(line, ",");
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while (token != NULL) {
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long long start, end;
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if (sscanf(token, "%lld-%lld", &start, &end) == 2)
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for (long long id = start; id <= end; id++) if (is_invalid_id(id)) total += id;
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token = strtok(NULL, ",");
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}
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free(line);
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printf("Part 1: %lld\n", total);
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}