POJ 3083 java实现

需要两次DFS+一次BFS
需要注意:
1.BFS记得Visit数组,对于访问过的节点,不要再加入到队列中,否则会内存溢出
2.DFS注意方向.以from-->to的方向为基准,标记好前后左右,再进行dfs.

以下是AC代码:

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayDeque;
import java.util.StringTokenizer;

public class Main {
    static boolean[][] isVisit;
    static char[][] road;
    static int ans, m, n;
    static boolean hasAns;

    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        int T = Integer.parseInt(st.nextToken());
        for (int testcase = 1; testcase <= T; testcase++) {
            st = new StringTokenizer(br.readLine());
            n = Integer.parseInt(st.nextToken());
            m = Integer.parseInt(st.nextToken());
            isVisit = new boolean[m][n];
            road = new char[m][n];
            String s;
            int startX = 0, startY = 0, endX = 0, endY = 0;
            for (int i = 0; i < m; i++) {
                s = br.readLine();
                road[i] = s.toCharArray();
                if (s.indexOf('S') != -1) {
                    startX = i;
                    startY = s.indexOf('S');
                }
                if (s.indexOf('E') != -1) {
                    endX = i;
                    endY = s.indexOf('S');
                }
            }
            ans = 0;
            hasAns = false;
            dfs(startX, startY, 'u');
            System.out.print(ans + " ");

            ans = 0;
            hasAns = false;
            dfs2(startX, startY, 'u');
            System.out.print(ans + " ");

            ans = 0;
            isVisit = new boolean[m][n];
            bfs(startX, startY);
            System.out.println(ans);
        }
    }

    private static void dfs(int x, int y, char direct) {
        ans++;
        if(hasAns){
            return;
        }
        if (road[x][y] == 'E') {
            hasAns = true;
            return;
        }
        if (direct == 'u') {
            if (y - 1 >= 0 && road[x][y - 1] != '#') {
                dfs(x, y - 1, 'l');
            } else if (x - 1 >= 0 && road[x - 1][y] != '#') {
                dfs(x - 1, y, 'u');
            } else if (y + 1 < n && road[x][y + 1] != '#') {
                dfs(x, y + 1, 'r');
            } else if (x + 1 < m && road[x + 1][y] != '#') {
                dfs(x + 1, y, 'd');
            }
        }
        else if (direct == 'l') {
            if (x + 1 < m && road[x + 1][y] != '#') {
                dfs(x + 1, y, 'd');
            } else if (y - 1 >= 0 && road[x][y - 1] != '#') {
                dfs(x, y - 1, 'l');
            } else if (x - 1 >= 0 && road[x - 1][y] != '#') {
                dfs(x - 1, y, 'u');
            } else if (y + 1 < n && road[x][y + 1] != '#') {
                dfs(x, y + 1, 'r');
            }
        }
        else if (direct == 'd') {
            if (y + 1 < n && road[x][y + 1] != '#') {
                dfs(x, y + 1, 'r');
            } else if (x + 1 < m && road[x + 1][y] != '#') {
                dfs(x + 1, y, 'd');
            } else if (y - 1 >= 0 && road[x][y - 1] != '#') {
                dfs(x, y - 1, 'l');
            } else if (x - 1 >= 0 && road[x - 1][y] != '#') {
                dfs(x - 1, y, 'u');
            }
        }
        else if (direct == 'r') {
            if (x - 1 >= 0 && road[x - 1][y] != '#') {
                dfs(x - 1, y, 'u');
            } else if (y + 1 < n && road[x][y + 1] != '#') {
                dfs(x, y + 1, 'r');
            } else if (x + 1 < m && road[x + 1][y] != '#') {
                dfs(x + 1, y, 'd');
            } else if (y - 1 >= 0 && road[x][y - 1] != '#') {
                dfs(x, y - 1, 'l');
            }
        }
    }

    private static void dfs2(int x, int y, char direct) {
        ans++;
        if(hasAns){
            return;
        }
        if (road[x][y] == 'E') {
            hasAns = true;
            return;
        }
        if (direct == 'u') {
            if (y + 1 < n && road[x][y + 1] != '#') {
                dfs2(x, y + 1, 'r');
            } else if (x - 1 >= 0 && road[x - 1][y] != '#') {
                dfs2(x - 1, y, 'u');
            } else if (y - 1 >= 0 && road[x][y - 1] != '#') {
                dfs2(x, y - 1, 'l');
            } else if (x + 1 < m && road[x + 1][y] != '#') {
                dfs2(x + 1, y, 'd');
            }
        }
        else if (direct == 'l') {
            if (x - 1 >= 0 && road[x - 1][y] != '#') {
                dfs2(x - 1, y, 'u');
            } else if (y - 1 >= 0 && road[x][y - 1] != '#') {
                dfs2(x, y - 1, 'l');
            } else if (x + 1 < m && road[x + 1][y] != '#') {
                dfs2(x + 1, y, 'd');
            } else if (y + 1 < n && road[x][y + 1] != '#') {
                dfs2(x, y + 1, 'r');
            }
        }
        else if (direct == 'd') {
            if (y - 1 >= 0 && road[x][y - 1] != '#') {
                dfs2(x, y - 1, 'l');
            } else if (x + 1 < m && road[x + 1][y] != '#') {
                dfs2(x + 1, y, 'd');
            } else if (y + 1 < n && road[x][y + 1] != '#') {
                dfs2(x, y + 1, 'r');
            } else if (x - 1 >= 0 && road[x - 1][y] != '#') {
                dfs2(x - 1, y, 'u');
            }
        }
        else if (direct == 'r') {
            if (x + 1 < m && road[x + 1][y] != '#') {
                dfs2(x + 1, y, 'd');
            } else if (y + 1 < n && road[x][y + 1] != '#') {
                dfs2(x, y + 1, 'r');
            } else if (x - 1 >= 0 && road[x - 1][y] != '#') {
                dfs2(x - 1, y, 'u');
            } else if (y - 1 >= 0 && road[x][y - 1] != '#') {
                dfs2(x, y - 1, 'l');
            }
        }
    }

    private static void bfs(int xx, int yy) {
        ArrayDeque<int[]> next = new ArrayDeque<int[]>();
        next.addLast(new int[]{xx, yy, 1});
        int[] poll;
        int x, y, dist;
        while (!next.isEmpty()) {
            poll = next.pollFirst();
            x = poll[0];
            y = poll[1];
            dist = poll[2];
            if (road[x][y] == 'E') {
                ans = dist;
                return;
            }
            if(isVisit[x][y]){
                continue;
            }
            isVisit[x][y] = true;
            if (x + 1 < m && road[x + 1][y] != '#' && !isVisit[x + 1][y]) {
                next.addLast(new int[]{x + 1, y, dist + 1});
            }
            if (y - 1 >= 0 && road[x][y - 1] != '#' && !isVisit[x][y - 1]) {
                next.addLast(new int[]{x, y - 1, dist + 1});
            }
            if (x - 1 >= 0 && road[x - 1][y] != '#' && !isVisit[x - 1][y]) {
                next.addLast(new int[]{x - 1, y, dist + 1});
            }
            if (y + 1 < n && road[x][y + 1] != '#' && !isVisit[x][y + 1]) {
                next.addLast(new int[]{x, y + 1, dist + 1});
            }
        }
    }
}