[Swift]LeetCode256.粉刷房子 $ Paint House

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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.

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有N排房子，每棟房子均可以塗上三種顏色中的一種：紅色、藍色或綠色。用某種顏色粉刷每棟房子的費用是不一樣的。你必須把全部的房子都漆成沒有兩個相鄰的房子有相同的顏色。

用一個n x 3的成本矩陣表示每棟房子塗上某種顏色的成本。例如， costs[0][0是用紅色粉刷房子0的成本；costs[1][2]是用綠色粉刷房子1的成本，等等……找出油漆全部房屋的最低成本。

注：

全部成本costs都是正整數。

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 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 }