31 lines
1000 B
C
31 lines
1000 B
C
#include <stdio.h>
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#include <stdlib.h>
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#include "hashset/hashset.h"
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// Originally, I used hashsets for this, which refused to work for me.
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// I would then find out that the implementation I was using hashes based on the pointer, not the value, so I just wrote a stupid lookup table.
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#define inputLength 1000000 // adjust expected length
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int main() {
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int position = 0;
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char line [10];
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int positions [inputLength]; // all initialized to 0
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while (1) {
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FILE* inputFile = fopen("input", "r");
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while (fgets(line, sizeof(line), inputFile)) {
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position += strtol(line, NULL, 10);
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// Because of part 1, we know that the numbers are steadily increasing.
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// Negative numbers are therefore skipped, as we know the repeated number to be positive.
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if (position > 0 && positions[position] == 1) {
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printf("%d\n", position);
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return 0;
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}
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positions[position] = 1;
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}
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}
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}
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