6th_december.java

class Solution
{
    //Function to find distance of nearest 1 in the grid for each cell.
    public int[][] nearest(int[][] grid)
    {
        // Code here
        int n=grid.length;
        int m=grid[0].length;
        boolean[][]vis=new boolean[n][m];
        Queue<int[]> q=new LinkedList<>();
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                if(grid[i][j]==1){
                    q.add(new int[]{i,j});
                    vis[i][j]=true;
                }
            }
        }
        int[][]ans=new int[n][m];
        int[][]dirs={{1,0},{0,1},{-1,0},{0,-1}};

        int dis=0;
        while(!q.isEmpty()){
            int sz=q.size();
            while(sz-->0){
                int[]idx=q.remove();
                int x=idx[0];
                int y=idx[1];
                ans[x][y]=dis;
                for(int[]dir:dirs){
                    int i=x+dir[0];
                    int j=y+dir[1];
                    if(i>=0 && j>=0 && i<n && j<m && !vis[i][j]){
                        q.add(new int[]{i,j});
                        vis[i][j]=true;
                    }
                }
            }
            dis++;
        }
        return ans;
    }
}