advent-of-code/2018/05/day5_2.c

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2018-12-05 22:18:11 +01:00
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
int isSameLetter(char a, char b) {
char diff = (a > b) ? a - b : b - a;
return diff == 32;
}
int processArray(char* input, int length) {
int outputLength = 0;
for (int i=0; i<length; i++) {
if (isSameLetter(input[i], input[i+1]) == 1) {
i++;
} else {
input[outputLength] = input[i];
outputLength++;
}
}
return outputLength;
}
int removeFromArray(char* input, int length, char x) {
int outLength = 0;
for (int i=0; i<length; i++) {
if (!(input[i] == x || input[i] == x + 32)) {
input[outLength] = input[i];
outLength++;
}
}
return outLength;
}
int main() {
struct stat stbuffer;
FILE *inputFile = fopen("input", "r");
fstat(fileno(inputFile), &stbuffer);
int inSize = stbuffer.st_size + 1;
char *input = malloc(inSize);
int smallest = 1e9;
char smallest_char;
for (char c='A'; c<='Z'; c++) {
fseek(inputFile, 0, 0);
fgets(input, inSize, inputFile);
int outLength = removeFromArray(input, inSize, c);
int lastLength;
do {
lastLength = outLength;
outLength = processArray(input, lastLength);
} while (lastLength != outLength);
outLength--;
if (outLength < smallest) {
smallest = outLength;
smallest_char = c;
}
printf("%c: %d\n", c, outLength);
}
printf("Removing %c results in length %d\n", smallest_char, smallest);
fclose(inputFile);
free(input);
return 0;
}