# Paint House II

here 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.

Could you solve it in O(nk) runtime?

Tips:

Code:

``````public class Solution {
public int minCostII(int[][] costs) {
if (costs == null || costs.length == 0 || costs[0] == null || costs[0].length == 0) {
return 0;
}
int[] store = new int[costs[0].length];
int pre1 = 0, pre2 = 0;
int min1 = 0, min2 = 0;
for (int i = 0; i < costs.length; i++) {
pre1 = min1;
pre2 = min2;
min1 = Integer.MAX_VALUE;
min2 = Integer.MAX_VALUE;
for (int j = 0; j < costs[0].length; j++) {
if (store[j] != pre1 || pre1 == pre2) {
store[j] = costs[i][j] + pre1;
}
else  store[j] = costs[i][j] + pre2;
if (store[j] <= min1) {
min2 = min1;
min1 = store[j];
}
else if (store[j] <= min2) {
min2 = store[j];
}
}
}
return min1;
}
}
``````