Find A Specific Pair In Matrix

def findMaxValue(mat, n):
    dp=[[0]*n for i in range(n)]
    dp[0][0]=mat[0][0]
    ans=float('-inf')
    for i in range(1,n):
        dp[i][0]=min(mat[i][0],dp[i-1][0])
        dp[0][i]=min(mat[0][i],dp[0][i-1])


    for i in range(1,n):
        for j in range(1,n):
            #dp[i][j]=min(dp[i][j-1],dp[i-1][j],mat[i][j])
            dp[i][j]=min(dp[i-1][j],dp[i][j-1],mat[i][j])
            ans=max(mat[i][j]-dp[i-1][j-1],ans)
   # print(dp)
    return ans
'''
In dp table we store the minimum value of submatrix 0,0 to i,j
ans=max(mat[i][j]-dp[i-1][j-1],ans) for all i,j
'''