Submission #552586

#	Time	Username	Problem	Language	Result	Execution time	Memory
552586		SmolBrain	Portals (BOI14_portals)	C++17	100 / 100	559 ms	31768 KiB

portals

// Om Namah Shivaya
// GM in 101 days

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define endl '\n'
#define pb push_back
#define conts continue
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "YES" << endl
#define no cout << "NO" << endl
#define ff first
#define ss second
#define ceil2(x,y) ((x+y-1) / (y))
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#ifndef ONLINE_JUDGE
#define debug(x) cout << #x <<" = "; print(x); cout << endl
#else
#define debug(x)
#endif

#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define rev(i,s,e) for(int i = s; i >= e; --i)
#define trav(i,a) for(auto &i : a)

bool iseven(ll n) {if ((n & 1) == 0) return true; return false;}

void print(ll t) {cout << t;}
void print(int t) {cout << t;}
void print(string t) {cout << t;}
void print(char t) {cout << t;}
void print(double t) {cout << t;}
void print(ld t) {cout << t;}

template <class T, class V> void print(pair <T, V> p);
template <class T> void print(vector <T> v);
template <class T> void print(set <T> v);
template <class T, class V> void print(map <T, V> v);
template <class T> void print(multiset <T> v);
template <class T, class V> void print(pair <T, V> p) {cout << "{"; print(p.ff); cout << ","; print(p.ss); cout << "}";}
template <class T> void print(vector <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";}
template <class T> void print(set <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";}
template <class T> void print(multiset <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";}
template <class T, class V> void print(map <T, V> v) {cout << "[ "; for (auto i : v) {print(i); cout << " ";} cout << "]";}
template<typename T> void amin(T &a, T b) { a = min(a, b); }
template<typename T> void amax(T &a, T b) { a = max(a, b); }

void usaco(string filename) {
    freopen((filename + ".in").c_str(), "r", stdin);
    freopen((filename + ".out").c_str(), "w", stdout);
}

const int MOD = 1e9 + 7;
const int maxn = 1e5 + 5;
const int inf1 = 1e9 + 5;
const ll inf2 = ll(1e18) + 5;

int nxtleft[1005][1005], nxtright[1005][1005], nxtup[1005][1005], nxtdown[1005][1005];
bool vis[1005][1005];
int dis[1005][1005], dis2[1005][1005];
int dx[4] = { -1, 1, 0, 0};
int dy[4] = {0, 0, -1, 1};

void solve(int test_case)
{
    // referred to: https://github.com/tmwilliamlin168/CompetitiveProgramming/blob/master/BtOI/14-Portals.cpp and the official editorial code
    // initially got WA cuz i misunderstood the problem statement (more like overlooked a particular case)

    int n, m; cin >> n >> m;
    vector<vector<char>> a(n + 5, vector<char>(m + 5, '#'));
    rep1(i, n) rep1(j, m) cin >> a[i][j];

    rep1(i, n) {
        stack<ll> st;
        rep(j, m + 2) {
            if (a[i][j] == '#') {
                while (!st.empty()) {
                    nxtright[i][st.top()] = j;
                    st.pop();
                }
            }
            else {
                st.push(j);
            }
        }

        while (!st.empty()) st.pop();

        rev(j, m + 1, 0) {
            if (a[i][j] == '#') {
                while (!st.empty()) {
                    nxtleft[i][st.top()] = j;
                    st.pop();
                }
            }
            else {
                st.push(j);
            }
        }
    }

    rep1(j, m) {
        stack<ll> st;

        rep(i, n + 2) {
            if (a[i][j] == '#') {
                while (!st.empty()) {
                    nxtdown[st.top()][j] = i;
                    st.pop();
                }
            }
            else {
                st.push(i);
            }
        }

        while (!st.empty()) st.pop();

        rev(i, n + 1, 0) {
            if (a[i][j] == '#') {
                while (!st.empty()) {
                    nxtup[st.top()][j] = i;
                    st.pop();
                }
            }
            else {
                st.push(i);
            }
        }
    }

    pii start, end;
    rep1(i, n) rep1(j, m) {
        if (a[i][j] == 'S') start = {i, j};
        else if (a[i][j] == 'C') end = {i, j};
    }

    queue<pii> q;
    rep(i, n + 2) rep(j, m + 2) {
        if (a[i][j] != '#') conts;
        q.push({i, j});
        vis[i][j] = 1;
        dis[i][j] = 0;
    }

    while (!q.empty()) {
        auto [i, j] = q.front();
        q.pop();

        rep(x, 4) {
            int i2 = i + dx[x], j2 = j + dy[x];
            if (i2 < 0 or i2 > n + 1 or j2 < 0 or j2 > m + 1) conts;
            if (vis[i2][j2]) conts;

            q.push({i2, j2});
            vis[i2][j2] = 1;
            dis[i2][j2] = dis[i][j] + 1;
        }
    }

    priority_queue< array<int, 3>, vector<array<int, 3>>, greater<array<int, 3>> > pq;
    memset(vis, 0, sizeof vis);
    rep(i, n + 5) rep(j, m + 5) dis2[i][j] = inf1;

    pq.push({0, start.ff, start.ss});
    dis2[start.ff][start.ss] = 0;

    while (!pq.empty()) {
        auto [cost, i, j] = pq.top();
        pq.pop();

        if (vis[i][j]) conts;
        vis[i][j] = 1;

        if (i == end.ff and j == end.ss) {
            cout << cost << endl;
            return;
        }

        rep(x, 4) {
            int i2 = i + dx[x], j2 = j + dy[x];
            if (i2 < 0 or i2 > n + 1 or j2 < 0 or j2 > m + 1) conts;
            if (vis[i2][j2]) conts;
            if (a[i2][j2] == '#') conts;

            if (cost + 1 < dis2[i2][j2]) {
                dis2[i2][j2] = cost + 1;
                pq.push({cost + 1, i2, j2});
            }
        }

        int min_dis_to_wall = dis[i][j];

        vector<pii> cells;
        cells.pb({i, nxtleft[i][j] + 1});
        cells.pb({i, nxtright[i][j] - 1});
        cells.pb({nxtup[i][j] + 1, j});
        cells.pb({nxtdown[i][j] - 1, j});

        for (auto [i2, j2] : cells) {
            int cost2 = cost + min_dis_to_wall;
            if (cost2 < dis2[i2][j2]) {
                dis2[i2][j2] = cost2;
                pq.push({cost2, i2, j2});
            }
        }
    }
}

int main()
{
    fastio;

    int t = 1;
    // cin >> t;
    rep1(i, t) {
        solve(i);
    }

    return 0;
}

Compilation message (stderr)

portals.cpp: In function 'void usaco(std::string)':
portals.cpp:64:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   64 |     freopen((filename + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
portals.cpp:65:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   65 |     freopen((filename + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 11 / 11
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 19 / 19
• Subtask 5: 30 / 30