Added medium problem

Author: das-jishu

Medium/minimum-passes-of-matrix.py

@@ -0,0 +1,61 @@
+
+# MINIMUM PASSES OF MATRIX
+
+# O(W * H) time and space
+def minimumPassesOfMatrix(matrix):
+    # Write your code here.
+    passes = convertNegatives(matrix)
+	return passes - 1 if not containsNegative(matrix) else -1
+
+def convertNegatives(matrix):
+	nextPassQueue = getAllPositivePositions(matrix)
+	
+	passes = 0
+	while len(nextPassQueue) > 0:
+		currentPassQueue = nextPassQueue
+		nextPassQueue = []
+		
+		while len(currentPassQueue) > 0:
+			row, column = currentPassQueue.pop(0)
+			adjacentPositions = getAdjacentPositions(row, column, matrix)
+			for position in adjacentPositions:
+				r, c = position
+				value = matrix[r][c]
+				if value < 0:
+					matrix[r][c] *= -1
+					nextPassQueue.append([r, c])
+
+		passes += 1
+	return passes
+
+def getAllPositivePositions(matrix):
+	positives = []
+	
+	for row in range(len(matrix)):
+		for col in range(len(matrix[row])):
+			value = matrix[row][col]
+			if value > 0:
+				positives.append([row, col])
+				
+	return positives
+
+def getAdjacentPositions(row, col, matrix):
+	adjacents = []
+	
+	if row > 0:
+		adjacents.append([row - 1, col])
+	if row < len(matrix) - 1:
+		adjacents.append([row + 1, col])
+	if col > 0:
+		adjacents.append([row, col - 1])
+	if col < len(matrix[0]) - 1:
+		adjacents.append([row, col + 1])
+		
+	return adjacents
+
+def containsNegative(matrix):
+	for row in matrix:
+		for value in row:
+			if value < 0:
+				return True
+	return False