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| #include <iostream>
#include <cstring>
#define INF 2000000000
using namespace std;
int n, holes[15][2], ans, pairing[7][2];
bool visit[15], check[8][2];
void makePair(int cur, int deep);
bool findCycle(int s, int o);
int main() {
cin >> n;
for (int i = 0; i < n; i++)
cin >> holes[i][0] >> holes[i][1];
visit[0] = true;
makePair(0, 0);
cout << ans;
}
void makePair(int cur, int deep) {
if (deep == n / 2) {
for (int i = 0; i < 2; i++) {
for (int j = 0; j < n / 2; j++)
if (findCycle(j, i)) {
ans++;
return;
}
}
return;
}
pairing[deep][0] = cur;
for (int i = cur + 1; i < n; i++) {
if (!visit[i]) {
visit[i] = true;
pairing[deep][1] = i;
int j = 0;
for (; j < n; j++)
if (!visit[j])
break;
visit[j] = true;
makePair(j, deep + 1);
visit[i] = false;
visit[j] = false;
}
}
}
bool findCycle(int s, int o) {
int next = pairing[s][!o];
check[s][o] = true;
while (next != -1) {
int cur = next;
next = -1;
int cr = holes[cur][1], cc = holes[cur][0], ni, nj, close = INF;
for (int i = 0; i < n / 2; i++) {
for (int j = 0; j < 2; j++) {
if (cr == holes[pairing[i][j]][1] && cc < holes[pairing[i][j]][0] && holes[pairing[i][j]][0] < close) {
close = holes[pairing[i][j]][0];
ni = i;
nj = j;
}
}
}
if (close != INF) {
if (check[ni][nj]) {
memset(check, 0, sizeof(check));
return true;
}
check[ni][nj] = true;
next = pairing[ni][!nj];
}
}
memset(check, 0, sizeof(check));
return false;
}
|
