# 1504. Count Submatrices With All Ones

https://leetcode.com/problems/count-submatrices-with-all-ones

## Description

Given a `rows * columns` matrix `mat` of ones and zeros, return how many **submatrices** have all ones.

**Example 1:**

```

**Input:** mat = [[1,0,1],
              [1,1,0],
              [1,1,0]]
**Output:** 13
**Explanation:**There are **6** rectangles of side 1x1.
There are **2** rectangles of side 1x2.
There are **3** rectangles of side 2x1.
There is **1** rectangle of side 2x2. 
There is **1** rectangle of side 3x1.
Total number of rectangles = 6 + 2 + 3 + 1 + 1 = **13.**
```

**Example 2:**

```

**Input:** mat = [[0,1,1,0],
              [0,1,1,1],
              [1,1,1,0]]
**Output:** 24
**Explanation:**
There are **8** rectangles of side 1x1.
There are **5** rectangles of side 1x2.
There are **2** rectangles of side 1x3. 
There are **4** rectangles of side 2x1.
There are **2** rectangles of side 2x2. 
There are **2** rectangles of side 3x1. 
There is **1** rectangle of side 3x2. 
Total number of rectangles = 8 + 5 + 2 + 4 + 2 + 2 + 1 = 24**.**
```

**Example 3:**

```

**Input:** mat = [[1,1,1,1,1,1]]
**Output:** 21
```

**Example 4:**

```

**Input:** mat = [[1,0,1],[0,1,0],[1,0,1]]
**Output:** 5
```

**Constraints:**

* `1 <= rows <= 150`
* `1 <= columns <= 150`
* `0 <= mat[i][j] <= 1`

## ac

```java
```
