Leetcode 265: Paint House II

There are a row of n houses, each house can be painted with one of the k colors. 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 k cost matrix. For example, costs[0][0] is the cost of painting house 0 with color 0; costs[1][2] is the cost of painting house 1 with color 2, and so on... Find the minimum cost to paint all houses.

Note:
All costs are positive integers.

Follow up:
Could you solve it in O(nk) runtime?

 

 1 public class Solution {
 2     public int MinCostII(int[,] costs) {
 3         if (costs == null || costs.GetLength(0) == 0) return 0;
 4         
 5         int houses = costs.GetLength(0), colors = costs.GetLength(1);
 6         
 7         var dp = new int[colors];
 8         
 9         for (int i = 0; i < houses; i++)
10         {
11             var tmp = new int[colors];
12             Array.Copy(dp, tmp, colors);
13             
14             for (int j = 0; j < colors; j++)
15             {
16                 if (i == 0)
17                 {
18                     dp[j] = costs[i, j];                    
19                 }
20                 else
21                 {
22                     int min = Int32.MaxValue;
23                     for (int k = 0; k < colors; k++)
24                     {
25                         if (k != j)
26                         {
27                             min = Math.Min(min, tmp[k]);
28                         }
29                     }
30 
31                     dp[j] = min + costs[i, j];
32                 }
33             }
34         }
35         
36         int result = Int32.MaxValue;
37         
38         for (int j = 0; j < colors; j++)
39         {
40             result = Math.Min(result, dp[j]);
41         }
42         
43         return result;
44     }
45 }

 

posted @ 2017-12-20 01:51  逸朵  阅读(107)  评论(0编辑  收藏  举报