坦克大战 nyoj248
2016-07-25 10:21
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坦克大战
时间限制:1000 ms | 内存限制:65535 KB难度:3
描述
Many of us had played the game "Battle city" in our childhood, and some people (like me) even often play it on computer now.
What we are discussing is a simple edition of this game. Given a map that consists of empty spaces, rivers, steel walls and brick walls only. Your task is to get a bonus as soon as possible suppose that no enemies will disturb you (See the following picture).
![](http://acm.nyist.net/JudgeOnline/admin/kind/attached/20110504202029_28920.jpg)
Your tank can't move through rivers or walls, but it can destroy brick walls by shooting. A brick wall will be turned into empty spaces when you hit it, however, if your shot hit a steel wall, there will be no damage to the wall. In each of your turns, you
can choose to move to a neighboring (4 directions, not 8) empty space, or shoot in one of the four directions without a move. The shot will go ahead in that direction, until it go out of the map or hit a wall. If the shot hits a brick wall, the wall will disappear
(i.e., in this turn). Well, given the description of a map, the positions of your tank and the target, how many turns will you take at least to arrive there?
输入The input consists of several test cases. The first line of each test case contains two integers M and N (2 <= M, N <= 300). Each of the following M lines contains N uppercase letters, each of which is one of 'Y' (you), 'T'
(target), 'S' (steel wall), 'B' (brick wall), 'R' (river) and 'E' (empty space). Both 'Y' and 'T' appear only once. A test case of M = N = 0 indicates the end of input, and should not be processed.
输出For each test case, please output the turns you take at least in a separate line. If you can't arrive at the target, output "-1" instead.
样例输入
3 4 YBEB EERE SSTE 0 0
样例输出
8
来源POJ
上传者
sadsad
题解
这道题求最短路,与以往bfs不同的是,这个遇到B的话,步数是加2;遇到E的话,加1;所以需要用优先队列
#include<stdio.h>
#include<queue>
#include<iostream>
#include<algorithm>
#include<string.h>
using namespace std;
#define MAXN 310
#define INF 0x3f3f3f3f
int dx[4]= {0,0,1,-1};
int dy[4]= {1,-1,0,0};
struct node
{
int x,y;
int step;//标记步子
friend bool operator<(node s1,node s2)
{
return s1.step>s2.step;
}
} p,temp;//结构体优先队列
int n,m,vis[MAXN][MAXN],sx,sy,ans;//sx,sy分别标记起点坐标的横纵坐标
char map[MAXN][MAXN];//标记地图
bool judge(node s)
{
if(s.x<0||s.x>=n||s.y<0||s.y>=m)//判断是否越界
return true;
if(map[s.x][s.y]=='R'||map[s.x][s.y]=='S'||vis[s.x][s.y])//判断是否能走
return true;
return false;
}
void bfs()
{
priority_queue<node>q;
memset(vis,0,sizeof(vis));
p.x=sx;
p.y=sy;
p.step=0;
vis[sx][sy]=1;
q.push(p);
while(!q.empty())
{
p=q.top();
q.pop();
if(map[p.x][p.y]=='T')//判断是否到达终点
{
ans=p.step;
return ;
}
for(int i=0; i<4; i++)//四个方向的查询
{
temp.x=p.x+dx[i];
temp.y=p.y+dy[i];
if(judge(temp))//判断是否可以走
continue;
if(map[temp.x][temp.y]=='B')
{
temp.step=p.step+2;
}
else
{
temp.step=p.step+1;
}
vis[temp.x][temp.y]=1;//走过了标记为1
q.push(temp);
}
}
}
int main()
{
while(scanf("%d%d",&n,&m)!=EOF)
{
if(n==0&&m==0)
return 0;
for(int i=0; i<n; i++)
{
scanf("%s",map[i]);
for(int j=0; j<m; j++)
{
if(map[i][j]=='Y')
{
sx=i;
sy=j;
}
}
}
ans=INF;
bfs();
if(ans!=INF)
printf("%d\n",ans);
else
printf("-1\n");
}
}
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