Submission #958640

#	Time	Username	Problem	Language	Result	Execution time	Memory
958640		yeediot	Portals (BOI14_portals)	C++17	100 / 100	651 ms	111828 KiB

portals

#include<bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define all(x) x.begin(),x.end()
#define pii pair<int,int>
#define pb push_back
#define sz(x) (int)(x.size())
#define chmin(x,y) x=min(x,y)
#define chmax(x,y) x=max(x,y)
#define vi vector<int>
#define vp vector<pii>
#define vvi vector<vi>
#define ykh mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count())
#define __lg(x) 63-__builtin_clzll(x)
#define pow2(x) (1LL<<x)
void __print(int x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}

template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifdef local
void setio(){freopen("/Users/iantsai/Library/Mobile Documents/com~apple~CloudDocs/cpp/Empty.md","r",stdin);}
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
void setio(){}
#define debug(x...)
#endif
void setIO(string s) {
    freopen((s + ".in").c_str(), "r", stdin);
    freopen((s + ".out").c_str(), "w", stdout);
}
struct line{
    int a,b;
    int operator()(const int x)const{
        return a*x+b;
    }
};
bool check(line l1,line l2,line l3){
    return (l3.b-l2.b)*(l1.a-l2.a)<=(l2.b-l1.b)*(l2.a-l3.a);
}
const int mxn=1005;
const int inf=1e9;
char g[mxn][mxn];
int pdis[mxn][mxn];
int dis[mxn][mxn];
int n,m;
vector<vector<vector<pii>>>adj(mxn,vector<vector<pii>>(mxn));
bool wall(int i,int j){
    return (i==0 or i==n+1 or j==0 or j==m+1 or g[i][j]=='#');
}
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};
pii st,ed;
void pre(){
    for(int i=1;i<=n;i++){
        int last=0;
        for(int j=1;j<=m;j++){
            if(g[i][j]=='#'){
                last=j;
                continue;
            }
            adj[i][j].pb({i,last+1});
            for(int k=0;k<4;k++){
                adj[i][j].pb({i+dx[k],j+dy[k]});
            }
        }
        last=m+1;
        for(int j=m;j>=1;j--){
            if(g[i][j]=='#'){
                last=j;
                continue;
            }
            adj[i][j].pb({i,last-1});
        }
    }
    for(int j=1;j<=m;j++){
        int last=0;
        for(int i=1;i<=n;i++){
            if(g[i][j]=='#'){
                last=i;
                continue;
            }
            adj[i][j].pb({last+1,j});
        }
        last=n+1;
        for(int i=n;i>=1;i--){
            if(g[i][j]=='#'){
                last=i;
                continue;
            }
            adj[i][j].pb({last-1,j});
        }
    }
}
void calc_near_portal(){
    queue<pii>q;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            pdis[i][j]=inf;
            if(wall(i-1,j) or wall(i+1,j) or wall(i,j-1) or wall(i,j+1)){
                pdis[i][j]=0;
                q.push({i,j});
            }
        }
    }
    while(sz(q)){
        auto [x,y]=q.front();
        q.pop();
        for(auto [nx,ny]:adj[x][y]){
            if(pdis[nx][ny]==inf){
                pdis[nx][ny]=pdis[x][y]+1;
                q.push({nx,ny});
            }
        }
    }
}
bool adjacent(int x,int y,int nx,int ny){
    return abs(nx-x)==1 or abs(ny-y)==1;
}
void dij(){
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            dis[i][j]=inf;
        }
    }
    dis[st.F][st.S]=0;
    priority_queue<tuple<int,int,int>,vector<tuple<int,int,int>>,greater<tuple<int,int,int>>>pq;
    pq.push({0,st.F,st.S});
    while(sz(pq)){
        auto [d,x,y]=pq.top();
        pq.pop();
        if(x==ed.F and y==ed.S){
            cout<<d<<'\n';
            break;
        }
        if(d>dis[x][y])continue;
        for(auto [nx,ny]:adj[x][y]){
            int cost=d;
            if(adjacent(x,y,nx,ny)){
                cost+=1;
            }
            else{
                cost+=pdis[x][y]+1;
            }
            if(cost<dis[nx][ny]){
                dis[nx][ny]=cost;
                pq.push({cost,nx,ny});
            }
        }
    }
}
signed main(){
    setio();
    ios::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    cin>>n>>m;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            cin>>g[i][j];
            pdis[i][j]=inf;
            if(g[i][j]=='S'){
                st={i,j};
            }
            if(g[i][j]=='C'){
                ed={i,j};
            }
        }
    }
    pre();
    calc_near_portal();
    dij();
}
 /*
 input:
 
 */















 

Compilation message (stderr)

portals.cpp: In function 'void setIO(std::string)':
portals.cpp:41:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   41 |     freopen((s + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
portals.cpp:42:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   42 |     freopen((s + ".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