1277. Count Square Submatrices with All Ones

README.md

@@ -345,6 +345,7 @@
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 | 1268 | Search Suggestions System | [Ruby](./algorithms/ruby/1268-search-suggestions-system.rb) | Medium |
 | 1269 | Number of Ways to Stay in the Same Place After Some Steps | [Ruby](./algorithms/ruby/1269-number-of-ways-to-stay-in-the-same-place-after-some-steps.rb) | Hard |
+| 1277 | Count Square Submatrices with All Ones | [Ruby](./algorithms/ruby/1277-count-square-submatrices-with-all-ones.rb) | Medium |
 | 1282 | Group the People Given the Group Size They Belong To | [Ruby](./algorithms/ruby/1282-group-the-people-given-the-group-size-they-belong-to.rb) | Medium |
 | 1287 | Element Appearing More Than 25% In Sorted Array | [Ruby](./algorithms/ruby/1287-element-appearing-more-than-25-in-sorted-array.rb) | Easy |
 | 1318 | Minimum Flips to Make a OR b Equal to c | [Ruby](./algorithms/ruby/1318-minimum-flips-to-make-a-or-b-equal-to-c.rb) | Medium |

algorithms/ruby/1277-count-square-submatrices-with-all-ones.rb

@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+# 1277. Count Square Submatrices with All Ones
+# Medium
+# https://leetcode.com/problems/count-square-submatrices-with-all-ones
+
+=begin
+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 <= matrix.length <= 300
+* 1 <= matrix[0].length <= 300
+* 0 <= matrix[i][j] <= 1
+=end
+
+# @param {Integer[][]} matrix
+# @return {Integer}
+def count_squares(matrix)
+  m, n = matrix.length, matrix[0].length
+  result = 0
+  (0...m).each { |i|
+    (0...n).each { |j|
+      if matrix[i][j] != 0 && i > 0 && j > 0
+        matrix[i][j] = 1 + [matrix[i - 1][j], matrix[i - 1][j - 1], matrix[i][j - 1]].min
+      end
+      result += matrix[i][j]
+    }
+  }
+  result
+end
+
+# **************** #
+#       TEST       #
+# **************** #
+
+require "test/unit"
+class Test_count_squares < Test::Unit::TestCase
+  def test_
+    assert_equal 15, count_squares([[0, 1, 1, 1], [1, 1, 1, 1], [0, 1, 1, 1]])
+    assert_equal 7, count_squares([[1, 0, 1], [1, 1, 0], [1, 1, 0]])
+  end
+end