# Hints

`a[i]`

is either `0`

or `1`

.
`a[i*] = 0`

. Is it now easy to find the solution?
Since the array elements are either 0 or 1, and `0 | 0 = 0`

and `0 | 1 = 1`

, hence, `0 | x = x`

. Hence, if you were to look at the `i*`

row, the entries would be something like

```
a[i*] | a[j] = 0 | a[j] = a[j]
```

Hence, you should be able to compute the entire array with just this one hint.

Now, what if I don’t give you the initial hint that `a[i*] = 0`

. Can you smartly figure out such an `i*`

?

No, it’s not ALWAYS true that all 1s in the matrix implies that all elements in the original array were 1.

There could be at max one zero in the array.

For example, `[1, 1, 1]`

and `[1, 0, 1]`

have the same matrix.

Since the problem asks us to print any array, we should be fine with assuming that all elements are 1. Note that this is one of the solution, not the only solution.

`mat[i][j]`

? What does that tell us?
`a[i] | a[j] = 0`

implies that BOTH `a[i]`

and `a[j]`

are 0. We were able to successfully locate, not one, but two 0s. Voila, instead of relying on someone else for the hint of `i*`

, we created our own hint. We know that the row corresponding to `i*`

is the answer.

Now, how to solve this if the array is not a binary array?