Codeforces Round #516 (Div. 2) D. Labyrinth ---- BFS+思維
阿新 • • 發佈:2018-12-15
做法:
- 優先選取列,然後在向左右擴充套件。
- 然鵝,有思路,卻不會處理,看了本場Rank1,有雙端佇列巧妙處理列和行的優先順序,才發現處理更簡潔+易懂。ORZ
- 我們優先將列放到隊首,因為列是不需要消耗步數的,然後再將左右放到隊尾,然後依次訪問+標記,即可。
AC程式碼:
#include<bits/stdc++.h>
#define IO ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0)
#define pb(x) push_back(x)
#define sz(x) (int)(x).size()
#define sc(x) scanf("%d",&x)
#define pr(x) printf("%d\n",x)
#define abs(x) ((x)<0 ? -(x) : x)
#define all(x) x.begin(),x.end()
#define mk(x,y) make_pair(x,y)
#define debug printf("!!!!!!\n")
#define fin freopen("in.txt","r",stdin)
#define fout freopen("out.txt","w",stdout)
using namespace std;
typedef long long ll;
typedef pair<int,int> PII;
const int mod = 1e9+7;
const double PI = 4*atan(1.0);
const int maxm = 1e8+5;
const int maxn = 2e3+5;
const int INF = 0x3f3f3f3f;
const ll LINF = 1ll<<62;
int n,m,sx,sy,nx,ny;
char mmap[maxn][maxn];
bool vis[maxn][maxn] ;
struct node
{
int x,y;
int nx,ny;
node(int x,int y,int nx,int ny){
this->x = x;
this->y = y;
this->nx = nx;
this->ny = ny;
}
};
deque<node> q;
int bfs()
{
int cnt = 0;
while(!q.empty())
{
node tmp = q.front();
q.pop_front();
int x = tmp.x,y = tmp.y;
int nx = tmp.nx,ny = tmp.ny;
if(vis[x][y]) continue;
vis[x][y] = 1;
cnt++;
if(x-1>0 && mmap[x-1][y]!='*') q.push_front(node(x-1,y,nx,ny));
if(x+1<=n && mmap[x+1][y]!='*') q.push_front(node(x+1,y,nx,ny));
if(y-1>0 && mmap[x][y-1]!='*' && nx) q.push_back(node(x,y-1,nx-1,ny));
if(y+1<=m && mmap[x][y+1]!='*'&& ny) q.push_back(node(x,y+1,nx,ny-1));
}
return cnt;
}
int main()
{
// fin;
IO;
cin>>n>>m>>sx>>sy>>nx>>ny;
for(int i=1;i<=n;i++)
cin>>mmap[i]+1;
q.push_front(node(sx,sy,nx,ny));
cout<<bfs()<<endl;
return 0;
}