USACO Magic Squares

Code

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/*
ID: wcr19961
PROG: msquare
LANG: C++11
*/
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
typedef long long LL;
const int maxn = 10;
const int maxm = 100330;
const int A[maxn] = {1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880};
int len[maxm], fa[maxm];
char p[maxm], s[maxm];
bool vis[maxm];
struct node {
int a[8], st;
node trans(int t) {
node k = *this;
if (t == 0) {
for (int i = 0; i < 4; ++i) {
swap(k.a[i], k.a[8 - i - 1]);
}
} else if (t == 1) {
for (int i = 3; i > 0; --i) {
swap(k.a[i], k.a[i - 1]);
swap(k.a[8 - i - 1], k.a[8 - i]);
}
} else {
swap(k.a[5], k.a[6]);
swap(k.a[2], k.a[5]);
swap(k.a[1], k.a[2]);
}
k.cantor();
return k;
}
int cantor() {
st = 0;
for (int i = 0; i < 8; ++i) {
int cnt = 0;
for (int j = i + 1; j < 8; ++j) {
if (a[i] > a[j]) {
++cnt;
}
}
st += cnt * A[7 - i];
}
return st;
}
} a;
int main() {
freopen("msquare.in", "r", stdin);
freopen("msquare.out", "w", stdout);
for (int i = 0; i < 8; ++i) {
scanf("%d", &a.a[i]);
}
int aim = a.cantor();
for (int i = 0; i < 8; ++i) {
a.a[i] = i + 1;
}
vis[a.cantor()] = true;
fa[a.st] = -1, len[a.st] = 0;
queue<node> q;
q.push(a);
while (!q.empty()) {
node k = q.front();
q.pop();
if (k.st == aim) {
printf("%d\n", len[aim]);
int cnt = 0;
while (fa[aim] != -1) {
s[cnt++] = p[aim];
aim = fa[aim];
}
for (int i = 0; i < cnt; ++i) {
putchar(s[cnt - i - 1]);
if (i % 60 == 59) {
puts("");
}
}
if (cnt == 0 || cnt % 60 != 0) {
puts("");
}
return 0;
}
for (int i = 0; i < 3; ++i) {
node x = k.trans(i);
if (!vis[x.st]) {
vis[x.st] = true;
len[x.st] = len[k.st] + 1;
fa[x.st] = k.st;
p[x.st] = i + 'A';
q.push(x);
}
}
}
return 0;
}

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