【SPOJ】1771 Yet Another N-Queen Problem

#include<cstdio>
#include<cstring>
#define MAXN 1000000
#define MAXM 3000
#define INF 0x7FFFFFFF
int L[MAXN], R[MAXN], U[MAXN], D[MAXN];
int H[MAXM], S[MAXM], C[MAXN], X[MAXN], Y[MAXN], Q[MAXM], ans[MAXM], pos[MAXM];
int n, size;
bool vis[MAXM];
void Init(int m) {
int i;
for (i = 0; i <= m; i++) {
R[i] = i + 1;
L[i + 1] = i;
U[i] = D[i] = i;
S[i] = 0;
}
R[m] = 0;
size = m + 1;
}
inline void Link(int r, int c, int row) {
D[size] = D[c];
U[size] = c;
U[D[c]] = size;
D[c] = size;
if (H[r] < 0)
H[r] = L[size] = R[size] = size;
else {
L[size] = H[r];
R[size] = R[H[r]];
L[R[H[r]]] = size;
R[H[r]] = size;
}
S[c]++;
X[size] = r;
Y[size] = row;
C[size++] = c;
}
void Remove(int c) {
int i, j;
L[R[c]] = L[c];
R[L[c]] = R[c];
for (i = D[c]; i != c; i = D[i]) {
for (j = R[i]; j != i; j = R[j]) {
U[D[j]] = U[j];
D[U[j]] = D[j];
S[C[j]]--;
}
}
}
void Resume(int c) {
int i, j;
R[L[c]] = L[R[c]] = c;
for (i = D[c]; i != c; i = D[i]) {
for (j = R[i]; j != i; j = R[j]) {
U[D[j]] = D[U[j]] = j;
S[C[j]]++;
}
}
}
bool Dance(int now) {
int i, j, temp, c;
if (now >= n) {
for (i = 0; i < n; i++)
ans[Y[pos[i]]] = Q[X[pos[i]]];
printf("%d", ans[1]);
for (i = 2; i <= n; i++)
printf(" %d", ans[i]);
putchar('\n');
return true;
}
if (R[0] == 0)
return false;
for (temp = INF,i = R[0]; i; i = R[i]) {
if (i > n)
break;
if (temp > S[i]) {
temp = S[i];
c = i;
}
}
Remove(c);
for (i = D[c]; i != c; i = D[i]) {
pos[now] = i;
for (j = R[i]; j != i; j = R[j])
Remove(C[j]);
if (Dance(now + 1))
return true;
for (j = L[i]; j != i; j = L[j])
Resume(C[j]);
vis[X[i]] = false;
}
Resume(c);
return false;
}
void Build(int r, int c, int &k, bool flag) {
int p1, p2, p3, p4;
p1 = r;
p2 = n + c;
p3 = n + n + r + c - 1;
p4 = 4 * n - 1 + r - c + n;
if (flag)
vis[p1] = vis[p2] = vis[p3] = vis[p4] = true;
if (flag || (!vis[p1] && !vis[p2] && !vis[p3] && !vis[p4])) {
H[++k] = -1;
Link(k, p1, r);
Link(k, p2, r);
Link(k, p3, r);
Link(k, p4, r);
Q[k] = c;
}
}
int main() {
int i, j, k;
while (~scanf("%d", &n)) {
Init(6 * n - 2);
memset(vis, false, sizeof(vis));
for (k = 0, i = 1; i <= n; i++) {
scanf("%d", &j);
if (j)
Build(i, j, k, true);
}
for (i = 1; i <= n; i++) {
for (j = 1; j <= n; j++)
Build(i, j, k, false);
}
Dance(0);
}
return 0;
}