2020/day15.c


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#include <stdio.h>
#include <stdlib.h>
int main(void) {
	static int turns[30000000];
	int turn = 1;
	int last, next;
	scanf("%d,", &last);
	while (0 < scanf("%d,", &next)) {
		turns[last] = turn;
		last = next;
		turn++;
	}
	while (turn != 2020) {
		if (turns[last]) {
			next = turn - turns[last];
		} else {
			next = 0;
		}
		turns[last] = turn;
		last = next;
		turn++;
	}
	printf("%d\n", last);
	while (turn != 30000000) {
		if (turns[last]) {
			next = turn - turns[last];
		} else {
			next = 0;
		}
		turns[last] = turn;
		last = next;
		turn++;
	}
	printf("%d\n", last);
}