# 1428. Leftmost Column with at Least a One

https://leetcode.com/problems/leftmost-column-with-at-least-a-one

## Description

_(This problem is an **interactive problem**.)_

A **row-sorted binary matrix** means that all elements are `0` or `1` and each row of the matrix is sorted in non-decreasing order.

Given a **row-sorted binary matrix** `binaryMatrix`, return _the index (0-indexed) of the **leftmost column** with a 1 in it_. If such an index does not exist, return `-1`.

**You can't access the Binary Matrix directly.** You may only access the matrix using a `BinaryMatrix` interface:

* `BinaryMatrix.get(row, col)` returns the element of the matrix at index `(row, col)` (0-indexed).
* `BinaryMatrix.dimensions()` returns the dimensions of the matrix as a list of 2 elements `[rows, cols]`, which means the matrix is `rows x cols`.

Submissions making more than `1000` calls to `BinaryMatrix.get` will be judged _Wrong Answer_. Also, any solutions that attempt to circumvent the judge will result in disqualification.

For custom testing purposes, the input will be the entire binary matrix `mat`. You will not have access to the binary matrix directly.

**Example 1:**

![](https://assets.leetcode.com/uploads/2019/10/25/untitled-diagram-5.jpg)

```
**Input:** mat = [[0,0],[1,1]]
**Output:** 0
```

**Example 2:**

![](https://assets.leetcode.com/uploads/2019/10/25/untitled-diagram-4.jpg)

```
**Input:** mat = [[0,0],[0,1]]
**Output:** 1
```

**Example 3:**

![](https://assets.leetcode.com/uploads/2019/10/25/untitled-diagram-3.jpg)

```
**Input:** mat = [[0,0],[0,0]]
**Output:** -1
```

**Example 4:**

![](https://assets.leetcode.com/uploads/2019/10/25/untitled-diagram-6.jpg)

```
**Input:** mat = [[0,0,0,1],[0,0,1,1],[0,1,1,1]]
**Output:** 1
```

**Constraints:**

* `rows == mat.length`
* `cols == mat[i].length`
* `1 <= rows, cols <= 100`
* `mat[i][j]` is either `0` or `1`.
* `mat[i]` is sorted in non-decreasing order.

## ac

```java
```
