[Swift]LeetCode256.粉刷房子 $ 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.

有N排房子，每栋房子都可以涂上三种颜色中的一种：红色、蓝色或绿色。用某种颜色粉刷每栋房子的费用是不同的。你必须把所有的房子都漆成没有两个相邻的房子有相同的颜色。

用一个n x 3的成本矩阵表示每栋房子涂上某种颜色的成本。例如， costs[0][0是用红色粉刷房子0的成本；costs[1][2]是用绿色粉刷房子1的成本，等等……找出油漆所有房屋的最低成本。

注：

所有成本costs都是正整数。

 1 class Solution {
 2     func minCost(_ costs:[[Int]]) -> Int{
 3         if costs.isEmpty || costs[0].isEmpty
 4         {
 5             return 0
 6         }
 7         var dp:[[Int]] = costs 
 8         for i in 1..<dp.count
 9         {
10             for j in 0..<3
11             {
12                 dp[i][j] += min(dp[i - 1][(j + 1) % 3],dp[i - 1][(j + 2) % 3])
13             }
14         }
15         return min(min(dp.last![0],dp.last![1]),dp.last![2])
16     }
17 }