89 lines
1.4 KiB
C
89 lines
1.4 KiB
C
#include <limits.h>
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#include <stdio.h>
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#include <stdlib.h>
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long egcd(long *x, long *y, long a, long b) {
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if (b == 0) {
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*x = 1;
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*y = 0;
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return a;
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}
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long x1, y1;
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long gcd = egcd(&x1, &y1, b, a % b);
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*x = y1;
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*y = x1 - (a / b) * y1;
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return gcd;
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}
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long modinv(long a, long m) {
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long x, y;
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long gcd = egcd(&x, &y, a, m);
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if (gcd != 1) {
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return -1;
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}
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if (x < 0) {
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return m + x;
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}
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return x;
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}
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int main(int argc, char *argv[]) {
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if (argc < 2) {
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printf("Usage: %s <input file>\n", argv[0]);
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return 0;
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}
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FILE *fp = fopen(argv[1], "r");
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if (fp == NULL) {
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printf("Could not open file %s\n", argv[1]);
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return 1;
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}
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int t;
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fscanf(fp, "%d\n", &t);
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int buses[100] = {0};
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int n = 0;
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while (fscanf(fp, "%d,", &buses[n++]) == 1 || fscanf(fp, "x,") == 0)
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;
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n--;
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fclose(fp);
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// Part 1
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int min = INT_MAX;
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int tmin = 0;
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for (int i = 0; i < n; ++i) {
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if (buses[i] == 0) {
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continue;
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}
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int x = buses[i] - t % buses[i];
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if (x < min) {
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min = x;
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tmin = i;
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}
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}
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printf("%d\n", min * buses[tmin]);
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// Part 2
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unsigned long N = 1;
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for (int i = 0; i < n; ++i) {
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if (buses[i] == 0) {
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continue;
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}
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N *= buses[i];
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}
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long x = 0;
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for (int i = 0; i < n; ++i) {
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if (buses[i] == 0) {
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continue;
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}
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long Ni = N / buses[i];
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x += (buses[i] - i) * modinv(Ni, buses[i]) * Ni;
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}
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printf("%ld\n", x % N);
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return 0;
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}
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