[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。

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class Solution {
    func minCost(_ costs:[[Int]]) -> Int{
        if costs.isEmpty || costs[0].isEmpty
        {
            return 0
        }
        var dp:[[Int]] = costs 
        for i in 1..<dp.count
        {
            for j in 0..<3
            {
                dp[i][j] += min(dp[i - 1][(j + 1) % 3], dp[i - 1][(j + 2) % 3])
            }
        }
        return min(min(dp.last![0], dp.last![1]), dp.last![2])
    }
}