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

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