Rotting Oranges (Leetcode 994)

Problem Link: https://leetcode.com/problems/rotting-oranges/

class Solution:
    def orangesRotting(self, grid: List[List[int]]) -> int:
        
        m=len(grid)
        n=len(grid[0])
        visited=[[False for i in range(n)] for j in range(m)]
        ans=0
        q=[]
        for i in range(m):
            for j in range(n):
                if(grid[i][j]==2):
                    q.insert(0,[i,j,0])
                    visited[i][j]=True
                elif(grid[i][j]==0):
                    visited[i][j]=True
                    
        
        while(len(q)>0):
            
            curr=q.pop()
            curri=curr[0]
            currj=curr[1]
            currtime=curr[2]
            
            
            
            ans=max(ans,currtime)
            
            if(curri-1>=0 and grid[curri-1][currj]==1 and visited[curri-1][currj]==False):
                visited[curri-1][currj]=True
                q.insert(0,[curri-1,currj,currtime+1])
            
            if(curri+1<m and grid[curri+1][currj]==1 and visited[curri+1][currj]==False):
                visited[curri+1][currj]=True
                q.insert(0,[curri+1,currj,currtime+1])
            
            if(currj-1>=0 and grid[curri][currj-1]==1 and visited[curri][currj-1]==False):
                visited[curri][currj-1]=True
                q.insert(0,[curri,currj-1,currtime+1])
            
            if(currj+1<n and grid[curri][currj+1]==1 and visited[curri][currj+1]==False):
                visited[curri][currj+1]=True
                q.insert(0,[curri,currj+1,currtime+1])
        
        # If any fresh oranges are left, return -1    
        for i in range(m):
            for j in range(n):
                if(visited[i][j]==0):
                    return -1
        else:
            return ans