# Paint House II

Paint House II dynamic programming
``````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 is the cost of painting house 0 with color 0; costs 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?

Paint House Ii Solution

``````public class PaintHouseII {
public int minCostII(int[][] costs) {
if(costs == null|| costs.length == 0) {
return 0;
}

int m = costs.length;
int n = costs.length;

int min1 = -1;
int min2 = -1;

for(int i = 0; i < m; i++) {
int last1 = min1;
int last2 = min2;

min1 = -1;
min2 = -1;

for(int j = 0; j < n; j++) {
if(j != last1) {
costs[i][j] += last1 < 0 ? 0 : costs[i - 1][last1];
} else {
costs[i][j] += last2 < 0 ? 0 : costs[i - 1][last2];
}

if(min1 < 0 || costs[i][j] < costs[i][min1]) {
min2 = min1;
min1 = j;
} else if(min2 < 0 || costs[i][j] < costs[i][min2]) {
min2 = j;
}
}
}

return costs[m - 1][min1];
}
}``````