(13)UniquePathIII

时间:2023-10-01 17:29:42

一、问题描述

给定一个二维数组。

  • 数组只有一个元素是1,是起点
  • 数组只有一个元素是2,是终点
  • 数组中的0是必须经过的地方
  • 数组中的-1是障碍不可通过

从起始点到终点一共有多少路径?

二、思路

DFS

三、Code

 package algorithm;

 /**
  * Created by adrian.wu on 2019/2/27.
  */
 public class UniquePathIII {
     private int sr, sc, er, ec, res, empty = 0;
     public int uniquePathIII(int[][] grid) {
         for (int i = 0; i < grid.length; i++) {
             for (int j = 0; j < grid[0].length; j++) {
                 if (grid[i][j] == 0) empty++;
                 else if (grid[i][j] == 1) {
                     sr = i;
                     sc = j;
                 }
                 else if (grid[i][j] == 2) {
                     er = i;
                     ec = j;
                     empty++;
                 }
             }
         }

         dfs(grid, sr, sc);
         return res;
     }

     private void dfs(int[][] grid, int i, int j) {
         if (!validRange(grid, i, j)) return;
         if (i == er && j == ec && empty == 0) {
             res++;
             return;
         }
         grid[i][j] = -2;
         empty--;
         dfs(grid, i + 1, j);
         dfs(grid, i - 1, j);
         dfs(grid, i, j + 1);
         dfs(grid, i, j - 1);
         grid[i][j] = 0;
         empty++;
     }

     private boolean validRange(int[][] grid, int i, int j) {
         return i >= 0 && i < grid.length && j >= 0 && j < grid[0].length && grid[i][j] >= 0;
     }

 }