256. Paint House

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.
Note:
All costs are positive integers.

Solution：DP

思路： 本house 分别以R G B 喷的情况
Time Complexity: O(N) Space Complexity: O(N)

Solution Code：

class Solution {
    public int minCost(int[][] costs) {
        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][1],costs[i-1][0]);
        }
        int n = costs.length-1;
        return Math.min(Math.min(costs[n][0], costs[n][1]), costs[n][2]);
    }
}