HDU 1072 Nightmare 題解

Nightmare

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 14260    Accepted Submission(s): 6930

Problem Description

Ignatius had a nightmare last night. He found himself in a labyrinth with a time bomb on him. The labyrinth has an exit, Ignatius should get out of the labyrinth before the bomb explodes. The initial exploding time of the bomb is set to 6 minutes. To prevent the bomb from exploding by shake, Ignatius had to move slowly, that is to move from one area to the nearest area(that is, if Ignatius stands on (x,y) now, he could only on (x+1,y), (x-1,y), (x,y+1), or (x,y-1) in the next minute) takes him 1 minute. Some area in the labyrinth contains a Bomb-Reset-Equipment. They could reset the exploding time to 6 minutes.

Given the layout of the labyrinth and Ignatius' start position, please tell Ignatius whether he could get out of the labyrinth, if he could, output the minimum time that he has to use to find the exit of the labyrinth, else output -1.

Here are some rules:
1. We can assume the labyrinth is a 2 array.
2. Each minute, Ignatius could only get to one of the nearest area, and he should not walk out of the border, of course he could not walk on a wall, too.
3. If Ignatius get to the exit when the exploding time turns to 0, he can't get out of the labyrinth.
4. If Ignatius get to the area which contains Bomb-Rest-Equipment when the exploding time turns to 0, he can't use the equipment to reset the bomb.
5. A Bomb-Reset-Equipment can be used as many times as you wish, if it is needed, Ignatius can get to any areas in the labyrinth as many times as you wish.
6. The time to reset the exploding time can be ignore, in other words, if Ignatius get to an area which contain Bomb-Rest-Equipment, and the exploding time is larger than 0, the exploding time would be reset to 6.

 

Input

The input contains several test cases. The first line of the input is a single integer T which is the number of test cases. T test cases follow.
Each test case starts with two integers N and M(1<=N,Mm=8) which indicate the size of the labyrinth. Then N lines follow, each line contains M integers. The array indicates the layout of the labyrinth.
There are five integers which indicate the different type of area in the labyrinth:
0: The area is a wall, Ignatius should not walk on it.
1: The area contains nothing, Ignatius can walk on it.
2: Ignatius' start position, Ignatius starts his escape from this position.
3: The exit of the labyrinth, Ignatius' target position.
4: The area contains a Bomb-Reset-Equipment, Ignatius can delay the exploding time by walking to these areas.

 

Output

For each test case, if Ignatius can get out of the labyrinth, you should output the minimum time he needs, else you should just output -1.

 

Sample Input

 

3
3 3
2 1 1
1 1 0
1 1 3
4 8
2 1 1 0 1 1 1 0
1 0 4 1 1 0 4 1
1 0 0 0 0 0 0 1
1 1 1 4 1 1 1 3
5 8
1 2 1 1 1 1 1 4
1 0 0 0 1 0 0 1
1 4 1 0 1 1 0 1
1 0 0 0 0 3 0 1
1 1 4 1 1 1 1 1

 

Sample Output

 

4

-1

13

Author　　Ignatius.L

 

 

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這道題目顯然是用bfs來作的

可是有幾點必需要考慮

由於存在時間歸零的狀況

因此一個點可能通過屢次

又由於時間歸零了事後

在這一點會有重複

因此將n=4的點標記爲走過便可

這樣最後若是到不了就會隊列會一直運行直到空

下面拿出我有超多註釋

誰都能看懂的代碼

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 1 //Author:LanceYu  2 #include<iostream>  3 #include<string>  4 #include<cstring>  5 #include<cstdio>  6 #include<fstream>  7 #include<iosfwd>  8 #include<sstream>  9 #include<fstream>  10 #include<cwchar>  11 #include<iomanip>  12 #include<ostream>  13 #include<vector>  14 #include<cstdlib>  15 #include<queue>  16 #include<set>  17 #include<ctime>  18 #include<algorithm>  19 #include<complex>  20 #include<cmath>  21 #include<valarray>  22 #include<bitset>  23 #include<iterator>  24 #define ll long long  25 using namespace std;  26 const double clf=1e-8;  27 //const double e=2.718281828;  28 const double PI=3.141592653589793;  29 const int MMAX=2147483647;  30 //priority_queue<int>p;  31 //priority_queue<int,vector<int>,greater<int> >pq;  32 int n,m,map[101][101];  33 int vis[101][101];  34 int dir[4][2]={{-1,0},{1,0},{0,1},{0,-1}};  35 struct node  36 {  37 int x,y,t,step;  38 };  39  40 int bfs(int a,int b,int x,int y)  41 {  42 int i;  43 queue<node> q;  44 while(!q.empty())  45  q.pop();  46 q.push(node{a,b,6,0});//開始也能回來再走一次vis保持0  47 while(!q.empty())  48  {  49 node t=q.front();  50  q.pop();  51 if(t.x==x&&t.y==y)  52 return t.step;  53 if(t.t<=1)//會爆炸的狀況扔掉   54 continue;  55 for(int i=0;i<4;i++)  56  {  57 int dx=t.x+dir[i][0];  58 int dy=t.y+dir[i][1];  59 if(dx>=0&&dy>=0&&dx<n&&dy<m&&!vis[dx][dy]&&(map[dx][dy]==1||map[dx][dy]==2)||map[dx][dy]==3)//2也有可能重複走過  60  {  61 q.push(node{dx,dy,t.t-1,t.step+1});//此處能夠重複走故vis不進行賦值  62  }  63 if(dx>=0&&dy>=0&&dx<n&&dy<m&&!vis[dx][dy]&&map[dx][dy]==4)  64  {  65 vis[dx][dy]=1;  66 q.push(node{dx,dy,6,t.step+1});//由於是直接歸零，不必重複走故直接把vis變成1  67  }  68  }  69  }  70 return -1;  71 }  72 int main()  73 {  74 int t,a,b,x,y;  75 cin>>t;  76 while(t--)  77  {  78 scanf("%d%d",&n,&m);  79 memset(vis,0,sizeof(vis));  80 for(int i=0;i<n;i++)  81  {  82 for(int j=0;j<m;j++)  83  {  84 scanf("%d",&map[i][j]);  85 if(map[i][j]==2)//記錄起點  86  {  87 a=i;  88 b=j;  89  }  90 if(map[i][j]==3)//記錄終點   91  {  92 x=i;  93 y=j;  94  }  95  }  96  }  97 int ans=bfs(a,b,x,y);  98 printf("%d\n",ans);  99  } 100 return 0; 101 }

Notes:思想要求較高

PS:筆者在作這道題的時候把bfs裏面的兩個判斷語句弄反了，WA了好屢次，可能這就是菜吧

2018-11-16　　05:09:49　　Author:LanceYu