Largest Submatrix with Equal Number of 0's and 1's

def maximumArea (mat, r, c):
    for i in range(r):
        for j in range(c):
            if not mat[i][j]:mat[i][j]=-1
    def zerosum(arr):
        d={0:-1}
        s=0
        ans=0
        for i in range(c):
            s+=arr[i]
            if s in d:ans=max(ans,i-d[s])
            else:d[s]=i
        return ans
    ans=0
    for i in range(r):
        arr=[0 for i in range(c)]
        for j in range(i,r):
            for k in range(c):
                arr[k]+=mat[j][k]
            h=j-i+1
            w=zerosum(arr)
            ans=max(ans,w*h)
    return ans