地下迷宫(bfs)

1.地下迷宫

思路：用广度优先搜索算法，即bfs，因为输入数据行数和列数为[3,10]，所在在搜索路径时，可以用x*10+y来表示其对应的坐标，并且将其加入对应的hash结点中。另一方面要求输出消耗最小的路径，所以队列使用优先级队列，保证每次从队列中取出的总是消耗最小的状态结点。而搜索时，防止重复搜索，用vis数组来表示是否已经访问过，并且访问时，如果出现越界或者能量值小于0时，可以不考虑这些状态结点

具体代码如下：

import java.util.Scanner;import java.io.PrintWriter;import java.io.FileInputStream;import java.io.BufferedInputStream;import java.io.OutputStreamWriter;import java.io.IOException;import java.util.Map;import java.util.HashMap;import java.util.Queue;import java.util.PriorityQueue;import java.util.Comparator;import java.util.List;import java.util.ArrayList;public class Main implements Runnable{    private Scanner cin;    private PrintWriter cout;    private boolean DEBUG =  true;    private int n, m, p;    private Map<Integer, StateNode> hm;    private Queue<StateNode> queue;    private int[][] matrix;    private boolean[][] vis;    private int[] dirx = {-1, 0, 1, 0};    private int[] diry = {0, 1, 0, -1};    private int[] dirp = {-3, -1, 0, -1};    class StateNode    {        int x, y, step, p, pre;        StateNode()        {            x = 0; y = 0; step = 0; p = 0; pre = -1;        }        StateNode(int x, int y, int step, int p, int pre)        {            this.x = x;            this.y = y;            this.step = step;            this.p = p;            this.pre = pre;        }    }    private void init()    {        try {            if (DEBUG) {                cin = new Scanner(new BufferedInputStream(new FileInputStream("f:\\OJ\\uva_in.txt")));            } else {                cin = new Scanner(new BufferedInputStream(System.in));            }            cout = new PrintWriter(new OutputStreamWriter(System.out));        } catch (IOException e) {            e.printStackTrace();;        }    }    private int hashVal(StateNode node)    {        return node.x * 10 + node.y;    }    private boolean isTarget(StateNode node)    {        return node.x == 0 && node.y == m - 1 && node.p >= 0;    }    private boolean is_impossible(int x, int y, int curp)    {        if (x < 0 || x >= n || y < 0 || y >= m || curp < 0 || matrix[x][y] == 0 || vis[x][y]) return true;        return false;    }    private boolean input()    {        if (!cin.hasNextInt()) return false;        n = cin.nextInt();        m = cin.nextInt();        p = cin.nextInt();        matrix = new int[n][m];        for (int i = 0; i < n; i++) {            for (int j = 0; j < m; j++) {                matrix[i][j] = cin.nextInt();            }        }        return true;    }    private  void solve()    {        StateNode node = new StateNode(0, 0, 0, p, -1);        hm = new HashMap<>();        Comparator<StateNode> cmp = new Comparator<StateNode>() {            @Override            public int compare(StateNode o1, StateNode o2) {                return o2.p - o1.p;            }        };        queue = new PriorityQueue<StateNode>(cmp);        queue.add(node);        hm.put(hashVal(node), node);        vis = new boolean[n][m];        int ans = -1;        while (!queue.isEmpty()) {            StateNode cur_node = queue.poll();            if (isTarget(cur_node)) {                ans = hashVal(cur_node);                break;            }            vis[cur_node.x][cur_node.y] = true;            for (int i = 0; i < 4; i++) {                int new_x = cur_node.x + dirx[i];                int new_y = cur_node.y + diry[i];                int new_p = cur_node.p + dirp[i];                int new_step = cur_node.step + 1;                if (is_impossible(new_x, new_y, new_p)) continue;                StateNode new_node = new StateNode(new_x, new_y, new_step, new_p, hashVal(cur_node));                queue.add(new_node);                hm.put(hashVal(new_node), new_node);            }        }        if (ans == -1) {            cout.println("Can not escape!");        } else {            List<Integer> path = new ArrayList<>();            while (ans != -1) {                path.add(ans);                ans = hm.get(ans).pre;            }            for (int i = path.size() - 1; i >= 0; i--) {                cout.print("[" + Integer.toString(path.get(i) / 10) + "," + Integer.toString(path.get(i) % 10) + "]");                if (i != 0) cout.print(',');            }        }        cout.flush();    }    public void run()    {        init();        while (input())        {            solve();        }    }    public static void main(String[] args)    {        new Thread(new Main()).start();    }}