old_contents: """Leetcode 256. Paint House (Premium)
  Easy
  
  URL: https://leetcode.com/problems/paint-house
  
  There are a row of n houses, each house can be painted with one of the three colors:
  red, blue or green. The cost of painting each house with a certain color is different.
  You have to paint all the houses such that no two adjacent houses have the same color.
  
  The cost of painting each house with a certain color is represented by a n x 3 cost
  matrix. For example, costs[0][0] is the cost of painting house 0 with color red;
  costs[1][2] is the cost of painting house 1 with color green, and so on.
  Find the minimum cost to paint all houses.
  
  Note:
  All costs are positive integers.
  
  Example:
  Input: [[17,2,17],[16,16,5],[14,3,19]]
  Output: 10
  Explanation: Paint house 0 into blue, paint house 1 into green, paint house 2 into blue.
  Minimum cost: 2 + 5 + 3 = 10.
  """
  
  class SolutionDp(object):
      def minCost(self, costs):
          """
          :type costs: List[List[int]]
          :rtype: int
  
          Time complexity: O(n).
          Space complexity: O(1).
          """
          if not costs:
              return 0
  
          n_houses = len(costs)
  
          for i in range(1, n_houses):
              # Accumulate painting costs of the other two houses.
              costs[i][0] += min(costs[i - 1][1], costs[i - 1][2])
              costs[i][1] += min(costs[i - 1][0], costs[i - 1][2])
              costs[i][2] += min(costs[i - 1][0], costs[i - 1][1])
  
          return min(costs[-1])
  
  
  def main():
      # Output: 10
      costs = [[17,2,17],
               [16,16,5],
               [14,3,19]]
      print SolutionDp().minCost(costs)
  
  
  if __name__ == '__main__':
      main()
  
new_contents: """Leetcode 256. Paint House (Premium)
  Easy
  
  URL: https://leetcode.com/problems/paint-house
  
  There are a row of n houses, each house can be painted with one of the three colors:
  red, blue or green. The cost of painting each house with a certain color is different.
  You have to paint all the houses such that no two adjacent houses have the same color.
  
  The cost of painting each house with a certain color is represented by a n x 3 cost
  matrix. For example, costs[0][0] is the cost of painting house 0 with color red;
  costs[1][2] is the cost of painting house 1 with color green, and so on.
  Find the minimum cost to paint all houses.
  
  Note:
  All costs are positive integers.
  
  Example:
  Input: [[17,2,17],[16,16,5],[14,3,19]]
  Output: 10
  Explanation: Paint house 0 into blue, paint house 1 into green, paint house 2 into blue.
  Minimum cost: 2 + 5 + 3 = 10.
  """
  
  class SolutionDp(object):
      def minCost(self, costs):
          """
          :type costs: List[List[int]]
          :rtype: int
  
          Time complexity: O(n).
          Space complexity: O(1).
          """
          if not costs:
              return 0
  
          n_houses = len(costs)
  
          # Start from house 1 to accumulate costs of the other two houses.
          for i in range(1, n_houses):
              costs[i][0] += min(costs[i - 1][1], costs[i - 1][2])
              costs[i][1] += min(costs[i - 1][0], costs[i - 1][2])
              costs[i][2] += min(costs[i - 1][0], costs[i - 1][1])
  
          return min(costs[-1])
  
  
  def main():
      # Output: 10
      costs = [[17,2,17],
               [16,16,5],
               [14,3,19]]
      print SolutionDp().minCost(costs)
  
  
  if __name__ == '__main__':
      main()
  
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