PaintHouse.java

/**
 * There are a row of n houses, each house can be painted with one of the three colors: red, blue or green. 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 3 cost matrix. For example, costs[0][0]
 * is the cost of painting house 0 with color red; costs[1][2] is the cost of painting house 1 with color green, and so
 * on... Find the minimum cost to paint all houses.
 */
public class PaintHouse {

    /**
     * @param costs n x 3 cost matrix
     * @return an integer, the minimum cost to paint all houses
     */
    public int minCost(int[][] costs) {
        // Write your code here
        if (costs == null || costs.length == 0)
            return 0;
        for (int i = 1; i < costs.length; i++) {
            costs[i][0] += Math.min(costs[i - 1][1], costs[i - 1][2]);
            costs[i][1] += Math.min(costs[i - 1][0], costs[i - 1][2]);
            costs[i][2] += Math.min(costs[i - 1][0], costs[i - 1][1]);
        }
        int last = costs.length - 1;
        return Math.min(costs[last][0], Math.min(costs[last][1], costs[last][2]));
    }

}