90 lines
1.9 KiB
C
90 lines
1.9 KiB
C
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#include <stdio.h>
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#include <string.h>
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#include <stdbool.h>
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#include <stdlib.h>
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int part_1(FILE *input) {
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rewind(input);
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char polymer[50001];
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fread(polymer, 50000, 1, input);
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bool changed = true;
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while(changed) {
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changed = false;
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for(int i = 0; i < 50000; i++) {
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if(polymer[i] == ' ') continue;
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for(int j = i + 1; j < 50000; j++) {
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if(polymer[j] == ' ') continue;
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if(polymer[i] == (polymer[j] + 'a' - 'A') || polymer[i] == (polymer[j] + 'A' - 'a') ) {
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polymer[i] = ' ';
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polymer[j] = ' ';
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changed = true;
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}
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break;
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}
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}
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}
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int count = 0;
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for(int i = 0; i < 50000; i++) {
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if(polymer[i] != ' ') count++;
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}
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return count;
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}
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int part_2(FILE *input) {
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char polymer[50001];
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int best_count = 50000;
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for(char to_remove = 'a'; to_remove <= 'z'; to_remove++) {
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rewind(input);
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fread(polymer, 50000, 1, input);
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for(int i = 0; i < 50000; i++) {
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if(polymer[i] == to_remove || polymer[i] == to_remove - 'a' + 'A') polymer[i] = ' ';
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}
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bool changed = true;
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while(changed) {
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changed = false;
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for(int i = 0; i < 50000; i++) {
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if(polymer[i] == ' ') continue;
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for(int j = i + 1; j < 50000; j++) {
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if(polymer[j] == ' ') continue;
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if(polymer[i] == (polymer[j] + 'a' - 'A') || polymer[i] == (polymer[j] + 'A' - 'a') ) {
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polymer[i] = ' ';
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polymer[j] = ' ';
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changed = true;
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}
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break;
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}
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}
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}
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int count = 0;
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for(int i = 0; i < 50000; i++) {
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if(polymer[i] != ' ') count++;
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}
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if(count < best_count) best_count = count;
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}
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return best_count;
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}
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int main() {
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char *input_file_path = "../data/2018/5/input.txt";
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FILE *input = fopen(input_file_path, "r");
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if (input == NULL) {
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printf("Can't open file %s\n", input_file_path);
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return 1;
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}
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printf("Part 1: %d\n", part_1(input));
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printf("Part 2: %d\n", part_2(input));
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fclose(input);
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}
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