Generate Random Path - Google Interview


http://www.1point3acres.com/bbs/thread-145576-1-1.html
就是给一个矩阵的size: n row, m column可选路径是每个格子周围的8个格 但不可以重复,
求生成一个从(0,0) 走到(n-1, m-1)的random 路径....
public class Solution {
        public static void main(String args[]){
                //int a[] = {7,2,4};
                Solution s = new Solution();
                int [][] result = s.getRandomPath(10, 10);
                for (int i = 0; i < result.length; i++){
                        for (int j = 0; j < result[0].length; j++){
                                System.out.print(result[i][j]+" ");
                        }
                        System.out.println();
                }
        }
       
          int [][]result;
          int m,n;
          int[][] getRandomPath(int n, int m){
              //check = new boolean[n][m];
              result = new int[n][m]; //all 0
              this.n = n;
              this.m = m;
              dfs(0,0,1);
              return result;
          }

          boolean dfs(int x, int y, int level){
            if (x < 0 || x >= n || y < 0 || y >= m || result[x][y] != 0){
                return false;
            }
            if (x == n-1 && y == m-1){
                result[x][y] = level;
                return true;
            }

            result[x][y] = level;
            boolean found = false;
            boolean[] directions = new boolean[8];
            Random randomGenerator = new Random();
            int totalCheck = 0;
            while (!found && totalCheck != 8){
              int random = randomGenerator.nextInt(8);
              if (directions[random]){ //skip checked direction
                continue;
              }
              totalCheck++;
              directions[random] = true;
              if (random == 0){
                found = dfs(x-1, y, level+1);
              }else if (random == 1){
                found = dfs(x+1, y, level+1);
              }else if (random == 2){
                found = dfs(x, y+1, level+1);
              }else if (random == 3){
                found = dfs(x, y-1, level+1);
              }else if (random == 4){
                found = dfs(x-1, y-1, level+1);
              }else if (random == 5){
                found = dfs(x+1, y+1, level+1);
              }else if (random == 6){
                found = dfs(x-1, y+1, level+1);
              }else{
                found = dfs(x+1, y-1, level+1);
              }
            }
            if (found){
              return true;
            }

            result[x][y] = 0;

            return false;
          }              
}

public class Leetcode {
        public static void main(String[] args){
                int[][] matrix = new int[10][10];
                List<Integer> result = new ArrayList<Integer>();
                if(fill(result, matrix, 0, 0))
                        System.out.print(result);
        }

        static boolean fill(List<Integer> result, int[][] matrix, int i, int j){
                int [] dx = {0,1,1,1,0,-1,-1,-1};
                int [] dy = {1,1,0,-1,-1,-1,0,1};
                if(i<0 || i>=matrix.length || j<0 || j>=matrix[0].length || matrix[i][j] != 0)
                        return false;
               
                matrix[i][j] = 1;
                result.add(matrix[0].length*i+j);
                if(i == matrix.length-1 && j == matrix[0].length-1)
                        return true;
                int [] directions = new int [8];
                Random randomGenerator = new Random();
                int count = 0;
                while(count != 8){
                        int random = randomGenerator.nextInt(8);
                        if(directions[random] == 1)
                                continue;
                        else{
                                directions[random] = 1;
                                count++;
                                if(fill(result, matrix, i+dx[random], j+dy[random]))
                                        return true;
                        }
                }
                result.remove(result.size()-1);
                matrix[i][j] = 0;
                return false;
        }
}

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