标签：each example htm etc solution ace ini nbsp ++
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?
这题的解法的思路还是用DP，但是在找不同颜色的最小值不是遍历所有不同颜色，而是用min1和min2来记录之前房子的最小和第二小的花费的颜色，如果当前房子颜色和min1相同，那么我们用min2对应的值计算，反之我们用min1对应的值，这种解法实际上也包含了求次小值的方法，感觉也是一种很棒的解题思路. (出处：http://www.cnblogs.com/grandyang/p/5322870.html)
细节：DP初始化后之后遍历都是从i = 1开始算的，不要重新算0，会错
实现：
class Solution { public int minCostII(int[][] costs) { if (costs == null || costs.length == 0 || costs[0].length == 0) { return 0; } int[][] dp = new int[costs.length][costs[0].length]; int preMin = Integer.MAX_VALUE; int preMinIdx = -1; int preMin2 = Integer.MAX_VALUE; for (int j = 0; j < costs[0].length; j++) { dp[0][j] = costs[0][j]; if (dp[0][j] < preMin) { preMin2 = preMin; preMin = dp[0][j]; preMinIdx = j; } else if (dp[0][j] < preMin2){ preMin2 = dp[0][j]; } } for (int i = 1; i < costs.length; i++) { int newPreMin = Integer.MAX_VALUE; int newPreMin2 = Integer.MAX_VALUE; int newPreMinIdx = -1; for(int j = 0; j < costs[0].length; j++) { if (j == preMinIdx) { dp[i][j] = costs[i][j] + preMin2; } else { dp[i][j] = costs[i][j] + preMin; } if (dp[i][j] < newPreMin) { newPreMin2 = newPreMin; newPreMin = dp[i][j]; newPreMinIdx = j; } else if (dp[i][j] < newPreMin2) { newPreMin2 = dp[i][j]; } } preMin = newPreMin; preMin2 = newPreMin2; preMinIdx = newPreMinIdx; } int result = Integer.MAX_VALUE; for (int j = 0; j < dp[0].length; j++) { result = Math.min(result, dp[dp.length - 1][j]); } return result; } }
leetcode265- Paint House II- hard
标签：each example htm etc solution ace ini nbsp ++
原文地址：http://www.cnblogs.com/jasminemzy/p/7842548.html
