1582. Special Positions in a Binary Matrix

Author: YuriSpiridonov

Easy/1582.SpecialPositionsinaBinaryMatrix.py

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+"""
+    Given a rows x cols matrix mat, where mat[i][j] is either 0 or 1, return 
+    the number of special positions in mat.
+
+    A position (i,j) is called special if mat[i][j] == 1 and all other elements 
+    in row i and column j are 0 (rows and columns are 0-indexed).
+
+    Example:
+    Input: mat = [[1,0,0],
+                  [0,0,1],
+                  [1,0,0]]
+    Output: 1
+    Explanation: (1,2) is a special position because mat[1][2] == 1 and all 
+                 other elements in row 1 and column 2 are 0.
+
+    Example:
+    Input: mat = [[1,0,0],
+                  [0,1,0],
+                  [0,0,1]]
+    Output: 3
+    Explanation: (0,0), (1,1) and (2,2) are special positions. 
+
+    Example:
+    Input: mat = [[0,0,0,1],
+                  [1,0,0,0],
+                  [0,1,1,0],
+                  [0,0,0,0]]
+    Output: 2
+
+    Example:
+    Input: mat = [[0,0,0,0,0],
+                  [1,0,0,0,0],
+                  [0,1,0,0,0],
+                  [0,0,1,0,0],
+                  [0,0,0,1,1]]
+    Output: 3
+
+    Constraints:
+        - rows == mat.length
+        - cols == mat[i].length
+        - 1 <= rows, cols <= 100
+        - mat[i][j] is 0 or 1.
+"""
+#Difficulty: Easy
+#95 / 95 test cases passed.
+#Runtime: 220 ms
+#Memory Usage: 13.9 MB
+
+#Runtime: 220 ms, faster than 48.49% of Python3 online submissions for Special Positions in a Binary Matrix.
+#Memory Usage: 13.9 MB, less than 61.78% of Python3 online submissions for Special Positions in a Binary Matrix.
+
+class Solution:
+
+    def numSpecial(self, mat: List[List[int]]) -> int:
+        count = 0
+        rows = len(mat)
+        cols = len(mat[0])
+        for row in range(rows):
+            for col in range(cols):
+                if mat[row][col] == 1 and self.rowCheck(mat, row) and self.colCheck(mat, rows, col):
+                    count += 1
+        return count
+
+    def rowCheck(self, mat, row):
+        return mat[row].count(1) == 1
+
+    def colCheck(self, mat, rows, col):
+        count = 0
+        for row in range(rows):
+            if mat[row][col] == 1:
+                count += 1
+        return count == 1