zoj1649-2022-3-28

Rescue

Time Limit: 2000 msMemory Limit: 65536 KB


7 8
#.#####.
#.a#…r.
#…#x…
…#…#.#
#…##…
.#…
…

TLE,深搜超时

#include<iostream>
#include<string.h>
#include<string>
#include<algorithm>

using namespace std;
char maps[205][205];
int visit[205][205];
int n,m,startx,starty;
int mint,len; 
//int dir[4][2]={{1,0},{0,-1},{-1,0},{0,1}}  //表示(x,y)的方向 

void dfs(int x,int y, int timelen)  //起点是angel，终点是朋友 
{
	if(timelen>=80000) return;
	if(x<0||x>=n||y<0||y>=m||visit[x][y]==1)
		return;
	if(timelen>=mint||maps[x][y]=='#')
	   return;
	if(maps[x][y]=='r')
	{
		if(timelen<mint)
		mint=timelen;
		return; 
	}
	if(maps[x][y]=='x') //碰到敌人相当于多走一步 
	{
		timelen++;
	}
	visit[x][y]=1;
	dfs(x+1,y,timelen+1);
	dfs(x-1,y,timelen+1);
	dfs(x,y+1,timelen+1);
	dfs(x,y-1,timelen+1);
	visit[x][y]=0;
}
int main()
{
	while(cin>>n>>m)//输入'EOF'停止
	{
		memset(visit,0,sizeof(visit));
		for(int i=0;i<n;i++)
		{
			cin>>maps[i];
			for(int j=0;j<m;j++)
			{
				if(maps[i][j]=='a')
				{
					startx=i;
					starty=j;
				} 
			}
		}
		len=0;
		mint=80000;
		dfs(startx,starty,len);
		if(mint<80000){
			cout<<mint<<endl;
		}
		else
		{
			cout<<"Poor ANGEL has to stay in the prison all his life."<<endl;
		}
	}
	return 0;
} 

换了 while(scanf("%d %d",&n,&m)!=EOF)//输入’EOF’停止
也是超时的。

所以这里换一个思路

用BFS来做，速度更快

#include<iostream>
#include<string.h>
#include<stdio.h>
#include<queue>
#include<algorithm>
using namespace std;
struct point
{
	int x;
	int y;
	int tl;   //目前时间 
	friend bool operator < (point a, point b)
	{
		return a.tl > b.tl;
	}
};

char maps[205][205];
int visit[205][205];
int n, m;
int dir[4][2] = { 1,0,-1,0,0,1,0,-1 }; //表示(x,y)的方向 

bool operator==(point a, point b)
{
	return(a.x == b.x && a.y == b.y);
}
void Bfs(point start, point end)  //起点是angel，终点是朋友 
{
	memset(visit, 0, sizeof(visit));
	start.tl = 0;
	int an = -1;
	priority_queue<point> q;
	q.push(start);
	visit[start.x][start.y] = 1;
	while (!q.empty())
	{
		point cur = q.top();
		q.pop();
		if (cur == end)  //因为是优先队列，所以 
		{
			an = cur.tl;
			break;
		}
		for (int i = 0; i < 4; i++)
		{
			point nep;
			nep.x = cur.x + dir[i][0];
			nep.y = cur.y + dir[i][1];
			if (nep.x < 0 || nep.x >= n || nep.y < 0 || nep.y >= m) continue;
			if (visit[nep.x][nep.y] == 1) continue;
			if (maps[nep.x][nep.y] == '#') continue;
			if (maps[nep.x][nep.y] == 'x')
			{
				nep.tl = cur.tl + 2;
			}
			else
			{
				nep.tl = cur.tl + 1;
			}
			q.push(nep);
			visit[nep.x][nep.y] = 1;
		}
	}
	if (an == -1) 	cout << "Poor ANGEL has to stay in the prison all his life." << endl;
	else cout << an << endl;
}

int main()
{
	while (cin>>n>>m)//输入'EOF'停止
	{
		int i = 0,j=0;
		point endpoint;
		point startp;
		memset(visit, 0, sizeof(visit));
		for (i=0; i < n; i++)
		{
			cin >> maps[i];
		}
		for(  i=0;i<n;i++)
		for (j = 0; j < m; j++)
			{
				if (maps[i][j] == 'a')
				{
					startp.x = i;
					startp.y = j;
				}
				if (maps[i][j] == 'r')
				{
					endpoint.x = i;
					endpoint.y = j;
				}
			}

		Bfs(startp, endpoint);
	}
	return 0;
}