Submission #956821

#	Time	Username	Problem	Language	Result	Execution time	Memory
956821		DeltaStruct	Mecho (IOI09_mecho)	C++17	84 / 100	181 ms	11816 KiB

mecho

#include <bits/stdc++.h>
using namespace std;
 
int main(){
#define int long long
  int n,m,inf=numeric_limits<int>::max(); cin >> n >> m; int sx,sy,gx,gy;
  vector<string> A(n); for (auto& a:A) cin >> a;
  queue<pair<int,int>> que; vector hd(n,vector<int>(n,inf));
  for (int i(0);i < n;++i) for (int k(0);k < n;++k){
    if (A[i][k]=='M') sx=i,sy=k;
    if (A[i][k]=='D') gx=i,gy=k;
    if (A[i][k]=='H') que.emplace(i,k),hd[i][k] = 0;
  }
  bool psf = true; auto can = [&psf,&A,&n](int x,int y){
    if (x==-1||x==n||y==-1||y==n) return false;
    if (A[x][y]=='T') return false;
    if (psf&&A[x][y]=='D') return false;
    return true;
  };
  while(!que.empty()){
    auto [i,k] = que.front(); que.pop();
    if (can(i+1,k)&&hd[i+1][k]==inf) hd[i+1][k]=hd[i][k]+m,que.emplace(i+1,k);
    if (can(i-1,k)&&hd[i-1][k]==inf) hd[i-1][k]=hd[i][k]+m,que.emplace(i-1,k);
    if (can(i,k+1)&&hd[i][k+1]==inf) hd[i][k+1]=hd[i][k]+m,que.emplace(i,k+1);
    if (can(i,k-1)&&hd[i][k-1]==inf) hd[i][k-1]=hd[i][k]+m,que.emplace(i,k-1);
  }
  psf = false; int l = -1,r = 1e9,mid;
  while(abs(l-r)>1){
    mid = (l+r)/2;
    vector dist(n,vector<int>(n,inf)); dist[sx][sy] = mid*m,que.emplace(sx,sy);
    while(!que.empty()){
      auto [i,k] = que.front(); que.pop();
      if (can(i+1,k)&&dist[i][k]+1<hd[i+1][k]&&dist[i+1][k]==inf) dist[i+1][k] = dist[i][k]+1,que.emplace(i+1,k);
      if (can(i-1,k)&&dist[i][k]+1<hd[i-1][k]&&dist[i-1][k]==inf) dist[i-1][k] = dist[i][k]+1,que.emplace(i-1,k);
      if (can(i,k+1)&&dist[i][k]+1<hd[i][k+1]&&dist[i][k+1]==inf) dist[i][k+1] = dist[i][k]+1,que.emplace(i,k+1);
      if (can(i,k-1)&&dist[i][k]+1<hd[i][k-1]&&dist[i][k-1]==inf) dist[i][k-1] = dist[i][k]+1,que.emplace(i,k-1);
    }
    if (dist[gx][gy]==inf) r = mid;
    else l = mid;
  }
  cout << l << endl;
}

Compilation message (stderr)

mecho.cpp: In function 'int main()':
mecho.cpp:38:20: warning: 'gy' may be used uninitialized in this function [-Wmaybe-uninitialized]
   38 |     if (dist[gx][gy]==inf) r = mid;
      |                    ^
mecho.cpp:38:16: warning: 'gx' may be used uninitialized in this function [-Wmaybe-uninitialized]
   38 |     if (dist[gx][gy]==inf) r = mid;
      |                ^

• Subtask 1: 84 / 100