牛客多校补题3
J
思路
模拟+搜索,比赛的时候就一个细节写错了
#include <bits/stdc++.h>
#define int long long
#define endl '\n'
using namespace std;
const int N = 5e5 + 10, mod = 1e9 + 7, INF = 0x3f3f3f3f3f3f3f3f;
int h[5*N], e[20 * N], ne[20 * N], idx;
int dist[5*N];
int a[N][5];
int n;
int s1, s2, t1, t2;
void add(int a, int b)
{
e[idx] = b, ne[idx] = h[a], h[a] = idx++;
}
struct node
{
int x, y, z;
};
void bfs()
{
map<pair<int, int>, int> mp;
deque<node> dq;
dq.push_back({s1, s2, 0});
while (dq.size())
{
auto it = dq.front();
dq.pop_front();
int x = it.x, y = it.y, z = it.z;
if (x == t1 && y == t2)
{
cout << z;
return;
}
if(mp[{x,y}])continue;
mp[{x, y}] = 1;
for (int j = 1; j <= 4; j++)
{
int p = a[y][j];
int w = j % 4 + 1;
if (p == x)
{
if (mp[{y, a[y][w]}] || a[y][w] == 0)
continue;
dq.push_front({y, a[y][w], z});
}
else
{
if (mp[{y, a[y][w]}] || a[y][w] == 0)
continue;
dq.push_back({y, a[y][w], z + 1});
}
}
}
cout << -1 << endl;
}
signed main()
{
ios::sync_with_stdio(false), cin.tie(nullptr);
memset(h, -1, sizeof h);
cin >> n;
for (int i = 1; i <= n; i++)
for (int j = 1; j <= 4; j++)
{
cin >> a[i][j];
if (!a[i][j])
continue;
add(i, a[i][j]);
add(a[i][j], i);
}
cin >> s1 >> s2 >> t1 >> t2;
bfs();
return 0;
}