256.cpp

/* 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. */

/* dp[i][j] = dp[i][j] + min(dp[i - 1][(j + 1) % 3], dp[i - 1][(j + 2) % 3])； */

class Solution {
public:
    int minCost(vector<vector<int>>& costs) {
        if (costs.empty() || costs[0].empty()) return 0;
        vector<vector<int>> dp = costs;
        for (int i = 1; i < dp.size(); ++i) {
            dp[i][0] += min(dp[i - 1][1], dp[i - 1][2]);
            dp[i][1] += min(dp[i - 1][0], dp[i - 1][2]);
            dp[i][2] += min(dp[i - 1][0], dp[i - 1][1]);
        }
        return min(min(dp.back()[0], dp.back()[1]), dp.back()[2]);
    }
};