OJ-Problems-Source/HDOJ/4850_autoAC.cpp

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#include <cstdio>
#include <cstring>
const int N = 20005;
int vis[N], vis2[N][30], on = 0;
char out[500005];
int getnext(int x, int a) {
return x % (26 * 26) * 26 + a;
}
void init() {
int now = 0;
for (int i = 0; i < 3; i++)
out[on++] = 'a';
while (true) {
int Min = 26, iv = 0;
for (int i = 1; i < 26; i++) {
if (vis2[now][i]) continue;
int tmp = getnext(now, i);
if (vis[tmp] < Min) {
Min = vis[tmp];
iv = i;
}
}
int tmp = getnext(now, iv);
if (vis[tmp] == 26) break;
vis2[now][iv] = 1;
now = tmp;
vis[now]++;
out[on++] = now % 26 + 'a';
}
}
int n;
int main() {
init();
while (~scanf("%d", &n)) {
if (n > 456979) printf("Impossible\n");
else printf("%s\n", (out + 456979 - n));
}
return 0;
}