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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define SZ 9
int *play(int *I, int C, int M)
{
int *c = malloc((C + 1) * sizeof(*c));
if (!c)
exit(1);
for (int i = 0; i < C; i++)
c[i] = i + 1;
for (int i = 0; i < C + 1; i++)
c[I[i]] = I[(i + 1) % SZ];
c[0] = I[0];
if (C > SZ) {
c[I[SZ - 1]] = SZ + 1;
c[C] = I[0];
}
for (int m = 1; m <= M; m++) {
int p1 = c[c[0]];
int p2 = c[c[c[0]]];
int p3 = c[c[c[c[0]]]];
int d = c[0] - 1 ? c[0] - 1 : C;
while (p1 == d || p2 == d || p3 == d)
d = d - 1 ? d - 1 : C;
c[c[0]] = c[p3];
c[p3] = c[d];
c[d] = p1;
c[0] = c[c[0]];
}
return c;
}
int main(int argc, char *argv[])
{
int data[] = { 4, 6, 3, 5, 2, 8, 1, 7, 9 };
int *d = malloc((1e6 + 1) * sizeof(*d));
memcpy(d, data, 9 * 4);
int *c = play(d, 1e6, 1e7);
long res = ((long)c[1]) * ((long)c[c[1]]);
printf("%lu\n", res);
free(d);
free(c);
return 0;
}
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