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1 | 1 | package com.fishercoder.solutions;
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2 | 2 |
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3 |
| -/** |
4 |
| - * 265. Paint House II |
5 |
| - * |
6 |
| - * There are a row of n houses, each house can be painted with one of the k colors. |
7 |
| - * The cost of painting each house with a certain color is different. |
8 |
| - * You have to paint all the houses such that no two adjacent houses have the same color. |
9 |
| - * The cost of painting each house with a certain color is represented by a n x k cost matrix. |
10 |
| - * |
11 |
| - * For example, costs[0][0] is the cost of painting house 0 with color 0; |
12 |
| - * costs[1][2] is the cost of painting house 1 with color 2, |
13 |
| - * and so on... |
14 |
| - * |
15 |
| - * Find the minimum cost to paint all houses. |
16 |
| -
|
17 |
| - Note: |
18 |
| - All costs are positive integers. |
19 |
| -
|
20 |
| - Follow up: |
21 |
| - Could you solve it in O(nk) runtime? |
22 |
| - */ |
23 | 3 | public class _265 {
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24 | 4 |
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25 |
| - public static class Solution1 { |
26 |
| - public int minCostII(int[][] costs) { |
27 |
| - if (costs == null || costs.length == 0) { |
28 |
| - return 0; |
29 |
| - } |
30 |
| - |
31 |
| - int n = costs.length; |
32 |
| - int k = costs[0].length; |
33 |
| - // min1 is the index of the 1st-smallest cost till previous house |
34 |
| - // min2 is the index of the 2nd-smallest cost till previous house |
35 |
| - int min1 = -1; |
36 |
| - int min2 = -1; |
37 |
| - |
38 |
| - for (int i = 0; i < n; i++) { |
39 |
| - int last1 = min1; |
40 |
| - int last2 = min2; |
41 |
| - min1 = -1; |
42 |
| - min2 = -1; |
43 |
| - |
44 |
| - for (int j = 0; j < k; j++) { |
45 |
| - if (j != last1) { |
46 |
| - // current color j is different to last min1 |
47 |
| - costs[i][j] += last1 < 0 ? 0 : costs[i - 1][last1]; |
48 |
| - } else { |
49 |
| - costs[i][j] += last2 < 0 ? 0 : costs[i - 1][last2]; |
50 |
| - } |
51 |
| - |
52 |
| - // find the indices of 1st and 2nd smallest cost of painting current house i |
53 |
| - if (min1 < 0 || costs[i][j] < costs[i][min1]) { |
54 |
| - min2 = min1; |
55 |
| - min1 = j; |
56 |
| - } else if (min2 < 0 || costs[i][j] < costs[i][min2]) { |
57 |
| - min2 = j; |
58 |
| - } |
59 |
| - } |
60 |
| - } |
61 |
| - return costs[n - 1][min1]; |
62 |
| - } |
63 |
| - } |
| 5 | + public static class Solution1 { |
| 6 | + public int minCostII(int[][] costs) { |
| 7 | + if (costs == null || costs.length == 0) { |
| 8 | + return 0; |
| 9 | + } |
| 10 | + |
| 11 | + int n = costs.length; |
| 12 | + int k = costs[0].length; |
| 13 | + // min1 is the index of the 1st-smallest cost till previous house |
| 14 | + // min2 is the index of the 2nd-smallest cost till previous house |
| 15 | + int min1 = -1; |
| 16 | + int min2 = -1; |
| 17 | + |
| 18 | + for (int i = 0; i < n; i++) { |
| 19 | + int last1 = min1; |
| 20 | + int last2 = min2; |
| 21 | + min1 = -1; |
| 22 | + min2 = -1; |
| 23 | + |
| 24 | + for (int j = 0; j < k; j++) { |
| 25 | + if (j != last1) { |
| 26 | + // current color j is different to last min1 |
| 27 | + costs[i][j] += last1 < 0 ? 0 : costs[i - 1][last1]; |
| 28 | + } else { |
| 29 | + costs[i][j] += last2 < 0 ? 0 : costs[i - 1][last2]; |
| 30 | + } |
| 31 | + |
| 32 | + // find the indices of 1st and 2nd smallest cost of painting current house i |
| 33 | + if (min1 < 0 || costs[i][j] < costs[i][min1]) { |
| 34 | + min2 = min1; |
| 35 | + min1 = j; |
| 36 | + } else if (min2 < 0 || costs[i][j] < costs[i][min2]) { |
| 37 | + min2 = j; |
| 38 | + } |
| 39 | + } |
| 40 | + } |
| 41 | + return costs[n - 1][min1]; |
| 42 | + } |
| 43 | + } |
64 | 44 |
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65 | 45 | }
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