256. Paint House

Easy

一道Easy的dp题，dp题如果简单能用O(1) space的时候就尽量优化。

class Solution {
    public int minCost(int[][] costs) {
        if (costs == null || costs.length == 0){
            return 0;
        }
        int n = costs.length;
        int curtRed = 0, curtBlue = 0, curtGreen = 0;
        for (int i = 0; i < n; i++){
            int lastRed = curtRed, lastBlue = curtBlue, lastGreen = curtGreen;
            curtRed = costs[i][0] + Math.min(lastBlue, lastGreen);
            curtBlue = costs[i][1] + Math.min(lastRed, lastGreen);
            curtGreen = costs[i][2] + Math.min(lastRed, lastBlue);
        }
        return Math.min(curtRed, Math.min(curtBlue, curtGreen));
    }
}