README.md

1277. Count Square Submatrices with All Ones

Given a m * n matrix of ones and zeros, return how many square submatrices have all ones.

Example 1:

Input: matrix =
[
  [0,1,1,1],
  [1,1,1,1],
  [0,1,1,1]
]
Output: 15
Explanation:
There are 10 squares of side 1.
There are 4 squares of side 2.
There is  1 square of side 3.
Total number of squares = 10 + 4 + 1 = 15.

Example 2:

Input: matrix =
[
  [1,0,1],
  [1,1,0],
  [1,1,0]
]
Output: 7
Explanation:
There are 6 squares of side 1.
There is 1 square of side 2.
Total number of squares = 6 + 1 = 7.

Constraints:

• 1 <= arr.length <= 300
• 1 <= arr[0].length <= 300
• 0 <= arr[i][j] <= 1

Solutions (Rust)

1. Solution

impl Solution {
    pub fn count_squares(mut matrix: Vec<Vec<i32>>) -> i32 {
        let mut ret = 0;

        for i in 0..matrix.len() {
            for j in 0..matrix[0].len() {
                if matrix[i][j] == 1 && i > 0 && j > 0 {
                    matrix[i][j] +=
                        matrix[i - 1][j - 1].min(matrix[i][j - 1].min(matrix[i - 1][j]));
                }

                ret += matrix[i][j];
            }
        }

        ret
    }
}