hdu 4198:Quick out of the Harbour解题报告
Quick out of the Harbour
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1441 Accepted Submission(s): 575
Problem Description
Captain Clearbeard decided to go to the harbour for a few days so his crew could inspect and repair the ship. Now, a few days later, the pirates are getting landsick(Pirates get landsick when they don't get enough of the ships' rocking motion. That's why pirates often try to simulate that motion by drinking rum.). Before all of the pirates become too sick to row the boat out of the harbour, captain Clearbeard decided to leave the harbour as quickly as possible.
Unfortunately the harbour isn't just a straight path to open sea. To protect the city from evil pirates, the entrance of the harbour is a kind of maze with drawbridges in it. Every bridge takes some time to open, so it could be faster to take a detour. Your task is to help captain Clearbeard and the fastest way out to open sea.
The pirates will row as fast as one minute per grid cell on the map. The ship can move only horizontally or vertically on the map. Making a 90 degree turn does not take any extra time.
Input
The first line of the input contains a single number: the number of test cases to follow. Each test case has the following format:
1. One line with three integers, h, w (3 <= h;w <= 500), and d (0 <= d <= 50), the height and width of the map and the delay for opening a bridge.
2.h lines with w characters: the description of the map. The map is described using the following characters:
—"S", the starting position of the ship.
—".", water.
—"#", land.
—"@", a drawbridge.
Each harbour is completely surrounded with land, with exception of the single entrance.
Output
For every test case in the input, the output should contain one integer on a single line: the travelling time of the fastest route to open sea. There is always a route to open sea. Note that the open sea is not shown on the map, so you need to move outside of the map to reach open sea.
Sample Input
2
6 5 7
#####
#S..#
#@#.#
#...#
#@###
#.###
4 5 3
#####
#S#.#
#@..#
###@#
Sample Output
16
11
这个题大概的意思就是一艘船要从S点出发，到达唯一出口的最短时间，只能走'.'（有水的地方）或者'@'标记的地方,不能走'#'标记的地方,因为有'.'花费的时间为1,'@'花费的时间为第三个参数c+1，所以考虑优先队列。
下面是暑假培训c++代码：
#include<iostream>
#include<cstdio>
#include<queue>
#include<string.h>
using namespace std;
char mp[502][502];
int vis[502][502];
int dir[][2]= {{1,0},{-1,0},{0,1},{0,-1}};
int n,m,c,ex,ey;
struct node
{
int x,y,step;
};
bool operator < (node t1,node t2)
{
return t1.step>t2.step;
}
priority_queue<node>q;
int bfs()
{
node t,next;
int tx;
while(!q.empty())
{
t=q.top();
q.pop();
if(t.x==ex&&t.y==ey) return t.step;
for(int i=0; i<4; i++)
{
next.step=t.step;
next.x=t.x+dir[i][0];
next.y=t.y+dir[i][1];
if(next.x<0||next.x>=n||next.y<0||next.y>=m||vis[next.x][next.y]||mp[next.x][next.y]=='#')
continue;
if(mp[next.x][next.y]=='@')
next.step+=(c+1);
if(mp[next.x][next.y]=='.')
next.step++;
vis[next.x][next.y]=1;
q.push(next);
}
}
return 0;
}
int main()
{
int tcase;
scanf("%d",&tcase);
while(tcase--)
{
node t;
memset(mp,0,sizeof(mp));
memset(vis,0,sizeof(vis));
while(!q.empty()) q.pop();
scanf("%d%d%d",&n,&m,&c);
for(int i=0; i<n; i++)
{
scanf("%s",mp[i]);
for(int j=0; j<m; j++)
{
if(mp[i][j]=='S')
{
t.x=i,t.y=j,t.step=0;
}
if((i==0||i==n-1||j==0||j==m-1)&&mp[i][j]!='#')
{
ex=i,ey=j;
}
}
}
q.push(t);
vis[t.x][t.y]=1;
printf("%d\n",bfs()+1);
}
return 0;
}
这里是最近写的JAVA代码（弄了好久，也积累了许多，发现class 和struct 不是一个东西，后面贴了个问题代码，有兴趣的朋友可以断点调试下，你会发现一个神奇的事情，也许是我觉得神奇吧，哈哈）有兴趣用JAVA写这种代码的人很少吧，我在网上搜都是用的c++，我就第一个吃螃蟹的人，也为以后需要的朋友提供个借鉴：
import java.util.PriorityQueue;
import java.util.Scanner;
public class Main {
static class node implements Comparable<node>{
int x, y, step;
public node(){
}
public node(int x,int y,int step){
this.x=x;
this.y=y;
this.step=step;
}
@Override
public int compareTo(node o) {
if(this.step>o.step) return 1;
return -1;
}
}
static int n, m, value;
static int startx, starty, endx, endy;
static char[][] map;
static boolean[][] visit;
static int dir[][] = { { 1, 0 }, { -1, 0 }, { 0, 1 }, { 0, -1 } };
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int tcase = sc.nextInt();
while (tcase-- > 0) {
n = sc.nextInt();
m = sc.nextInt();
value = sc.nextInt();
map = new char[n][m];
visit = new boolean[n][m];
for (int i = 0; i < n; i++) {
String str = sc.next();
map[i] = str.toCharArray();
for (int j = 0; j < m; j++) {
if (map[i][j] == 'S') {
startx = i;
starty = j;
}
if (map[i][j] != '#'
&& (i == 0 || i == n - 1 || j == 0 || j == m - 1)) {
endx = i;
endy = j;
}
}
}
System.out.println(BFS(startx,starty));
}
}
private static int BFS(int startx2, int starty2) {
PriorityQueue<node> q =new PriorityQueue<node>();
node t = new node(startx2,starty2,1); //step初始值为1,S点也要算进去
q.add(t);
visit[t.x][t.y]=true;
while(!q.isEmpty()){
t = q.remove();
if(t.x==endx&&t.y==endy) {
return t.step;
}
for(int i=0;i<4;i++){
int step = t.step;
int x = t.x+dir[i][0];
int y = t.y+dir[i][1];
if(x<0||x>n-1||y<0||y>m-1||visit[x][y]||map[x][y]=='#') continue;
if(map[x][y]=='@'){
step+=(value+1);
}
if(map[x][y]=='.'){
step++;
}
visit[x][y]=true;
q.add(new node(x,y,step));
}
}
return 0;
}
}
问题代码：
//问题代码
import java.util.PriorityQueue;
import java.util.Scanner;
public class Main {
static class node implements Comparable<node>{
int x, y, step;
@Override
public int compareTo(node o) {
if(this.step>o.step) return 1;
return -1;
}
}
static int n, m, value;
static int startx, starty, endx, endy;
static int[][] map;
static boolean[][] visit;
static int dir[][] = { { 1, 0 }, { -1, 0 }, { 0, 1 }, { 0, -1 } };
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int tcase = sc.nextInt();
while (tcase-- > 0) {
n = sc.nextInt();
m = sc.nextInt();
value = sc.nextInt();
map = new int[n][m];
visit = new boolean[n][m];
for (int i = 0; i < n; i++) {
String str = sc.next();
char[] x = str.toCharArray();
for (int j = 0; j < m; j++) {
if (x[j] == 'S') {
startx = i;
starty = j;
map[i][j] = 1;
}
if (x[j] == '@') {
map[i][j] = value+ 1;
}
if (x[j] == '#') {
map[i][j] = -1;
}
if (x[j] == '.') {
map[i][j] = 1;
}
if (x[j] != '#'
&& (i == 0 || i == n - 1 || j == 0 || j == m - 1)) {
endx = i;
endy = j;
map[i][j] = 0;
}
}
}
System.out.println(BFS(startx,starty));
}
}
private static int BFS(int startx2, int starty2) {
PriorityQueue<node> q =new PriorityQueue<node>();
node t = new node();
t.x=startx;
t.y=starty;
t.step = 0;
q.add(t);
visit[t.x][t.y]=true;
while(!q.isEmpty()){
t = q.remove();
//System.out.println(t.x+" "+t.y+" "+t.step);
if(t.x==endx&&t.y==endy) {
return t.step;
}
node t1 = new node();
for(int i=0;i<4;i++){
t1.step = t.step;
t1.x = t.x+dir[i][0];
t1.y = t.y+dir[i][1];
if(t1.x<0||t1.x>n-1||t1.y<0||t1.y>m-1||visit[t1.x][t1.y]||map[t1.x][t1.y]==-1) continue;
t1.step +=map[t1.x][t1.y];
//System.out.println("t1:"+t1.x+" "+t1.y+" "+t1.step);
visit[t1.x][t1.y]=true;
q.add(t1);
//System.out.println(q.peek().x+" "+q.peek().y+" "+q.peek().step);
}
}
return 0;
}
}
