Submission #106879

#	Time	Username	Problem	Language	Result	Execution time	Memory
106879		wilwxk	Portals (BOI14_portals)	C++11	0 / 100	65 ms	47608 KiB

portals

#include <bits/stdc++.h>
using namespace std;

const int MAXN=1e6+5;
const int MAXNN=1e3+3;
vector<int> g[MAXN], pes[MAXN];
set<pair<int, int> > s;
int ori[MAXNN][MAXNN];
int parede[5][MAXNN][MAXNN];
int dist[MAXN];
int n, nn, mm, star, chegada;

int quem(int i, int j) {
	return (i-1)*mm+j;
}
void liga(int a, int b, int c, int k) {
	if(a==b) return;
	// printf("%d liga %d c/ %d\n", a, b, c);
	g[a].push_back(b); if(k) g[b].push_back(a);
	pes[a].push_back(c); if(k) pes[b].push_back(c);
}

void dijkstra(int star) {
	for(int i=1; i<=n; i++) {
		dist[i]=1e9+9; if(i==star) dist[i]=0; 
		s.insert({dist[i], i});
	}
	while(!s.empty()) {
		int cur=s.begin()->second;
		if(cur==chegada) return;
		// printf("cur %d // %d\n", cur, dist[cur]);
		s.erase(s.begin());
		for(int i=0; i<g[cur].size(); i++) {
			int viz=g[cur][i]; int peso=pes[cur][i];
			// printf("  // %d > %d\n", viz, peso);
			if(dist[viz]>dist[cur]+peso) {
				s.erase({dist[viz], viz});
				dist[viz]=dist[cur]+peso;
				s.insert({dist[viz], viz});
			}
		}
	}
}

int main() {
	scanf("%d %d", &nn, &mm);
	for(int i=1; i<=nn; i++) {
		char cc[MAXNN]; scanf(" %s", &cc[1]);
		for(int j=1; j<=mm; j++) {
			char c=cc[j];
			if(c=='#') ori[i][j]=1;
			else ori[i][j]=0;
			if(c=='S') star=quem(i, j);
			if(c=='C') chegada=quem(i, j);
		}
	}

	for(int i=1; i<=nn; i++) {
		int ult=1;
		for(int j=1; j<=mm; j++) {
			if(ori[i][j]!=0) { ult=j+1; continue; }
			parede[1][i][j]=ult;

			if(i-1>=1&&ori[i-1][j]==0) liga(quem(i-1, j), quem(i, j), 1, 1);
			if(i+1<=nn&&ori[i+1][j]==0) liga(quem(i+1, j), quem(i, j), 1, 1);
			if(j-1>=1&&ori[i][j-1]==0) liga(quem(i, j-1), quem(i, j), 1, 1);
			if(j+1<=mm&&ori[i][j+1]==0) liga(quem(i, j+1), quem(i, j), 1, 1);
		}
		ult=mm;
		for(int j=mm; j>=1; j--) {
			if(ori[i][j]!=0) { ult=j-1; continue; }
			parede[2][i][j]=ult;
		}
	}

	for(int j=1; j<=mm; j++) {
		int ult=1;
		for(int i=1; i<=mm; i++) {
			if(ori[i][j]!=0) { ult=i+1; continue; }
			parede[3][i][j]=ult;
		}
		ult=nn;
		for(int i=nn; i>=1; i--) {
			if(ori[i][j]!=0) { ult=i-1; continue; }
			parede[4][i][j]=ult;
		}
	}

	for(int i=1; i<=nn; i++) {
		for(int j=1; j<=mm; j++) {
			if(ori[i][j]!=0) continue;
			int aa=abs(parede[1][i][j]-j);
			int bb=abs(parede[2][i][j]-j);
			int cc=abs(parede[3][i][j]-i);
			int dd=abs(parede[4][i][j]-i);
			int melhor=min(min(aa, bb), min(cc, dd))+1;

			int cur=quem(i, j);
			liga(cur, quem(i, parede[1][i][j]), min(melhor, aa), 0);
			liga(cur, quem(i, parede[2][i][j]), min(melhor, bb), 0);
			liga(cur, quem(parede[3][i][j], j), min(melhor, cc), 0);
			liga(cur, quem(parede[4][i][j], j), min(melhor, dd), 0);
		}
	}

	n=nn*mm;
	dijkstra(star);
	// for(int i=1; i<=n; i++) printf("%d > %d\n", i, dist[i]);

	printf("%d\n", dist[chegada]);

}

Compilation message (stderr)

portals.cpp: In function 'void dijkstra(int)':
portals.cpp:33:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0; i<g[cur].size(); i++) {
                ~^~~~~~~~~~~~~~
portals.cpp: In function 'int main()':
portals.cpp:46:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &nn, &mm);
  ~~~~~^~~~~~~~~~~~~~~~~~~
portals.cpp:48:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   char cc[MAXNN]; scanf(" %s", &cc[1]);
                   ~~~~~^~~~~~~~~~~~~~~

• Subtask 1: 0 / 11
• Subtask 2: 0 / 20
• Subtask 3: 0 / 20
• Subtask 4: 0 / 19
• Subtask 5: 0 / 30