994. Rotting Oranges

In a given grid, each cell can have one of three values:

the value 0 representing an empty cell;
the value 1 representing a fresh orange;
the value 2 representing a rotten orange.
Every minute, any fresh orange that is adjacent (4-directionally) to a rotten orange becomes rotten.

Return the minimum number of minutes that must elapse until no cell has a fresh orange. If this is impossible, return -1 instead.

Example 1:

Input: [[2,1,1],[1,1,0],[0,1,1]]
Output: 4
Example 2:

Input: [[2,1,1],[0,1,1],[1,0,1]]
Output: -1
Explanation: The orange in the bottom left corner (row 2, column 0) is never rotten, because rotting only happens 4-directionally.
Example 3:

Input: [[0,2]]
Output: 0
Explanation: Since there are already no fresh oranges at minute 0, the answer is just 0.

Note:

1 <= grid.length <= 10
1 <= grid[0].length <= 10
grid[i][j] is only 0, 1, or 2.

24 ms 38.6 MB

class Solution {
    public int orangesRotting(int[][] grid) {
        if(this.nothing(grid)){
            return 0;
        }
        if(this.neverR(grid)){
            return -1;
        }
        
        int count = 0;
        while(!this.isAllR(grid)){
            grid = this.infect(grid);

            count ++;
            if(count > grid.length * grid[0].length){
                return -1;
            }
        }
        return count;
    }
    
    public int[][] infect(int[][] grid){
        int[][] next = new int[grid.length][grid[0].length];
        for(int x  = 0; x < grid.length; x ++){
            for(int y = 0; y < grid[0].length; y++){
                next[x][y] = grid[x][y];
            }
        }
        for(int x  = 0; x < grid.length; x ++){
            for(int y = 0; y < grid[0].length; y++){
                if(grid[x][y] == 2){
                    if(x>0 && next[x-1][y] > 0){
                        next[x-1][y] = 2;
                    }
                    if(y>0 && next[x][y-1] > 0){
                        next[x][y-1] = 2;
                    }
                    if(x< grid.length-1 && next[x+1][y] > 0){
                        next[x+1][y] = 2;
                    }
                    if(y < grid[0].length - 1 && next[x][y+1] > 0){
                        next[x][y+1] = 2;
                    }
                }
            }
        }
        return next;
    }
    
    public boolean isAllR(int[][] grid){
        boolean allR = true;
        for (int[] col : grid){
            for (int c : col){
                if(c == 1){
                    allR = false;
                }
            }
        }
        return allR;
    }
    
    public boolean neverR(int[][] grid){
        boolean allFresh = true;
        for(int x  = 0; x < grid.length; x ++){
            for(int y = 0; y < grid[0].length; y++){

                if(grid[x][y] == 2){
                    allFresh = false;
                }
                
                if(grid[x][y] == 1){
                    
                    boolean alone = true;
                    if(x>0 && grid[x-1][y] != 0){
                        alone = false;
                    }
                    if(y>0 && grid[x][y-1] != 0){
                        alone = false;
                    }
                    if(x< grid.length-1 && grid[x+1][y] != 0){
                        alone = false;
                    }
                    if(y < grid[0].length - 1 && grid[x][y+1] != 0){
                        alone = false;
                    }
                    System.out.println(alone);
                    if(alone){
                        return true;
                    }
                }
            }
        }
        return allFresh;
    }
    
    
    public boolean nothing(int[][] grid){
        boolean nothing = true;
        for(int x  = 0; x < grid.length; x ++){
            for(int y = 0; y < grid[0].length; y++){

                if(grid[x][y] > 0){
                    nothing = false;
                }

            }
        }
        return nothing;
    }
}

 

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