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Leetcode256-paintHouse

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Solution Report of LeetCode Acceptted

Description

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.

Example

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Input: [[17,2,17],[16,16,5],[14,3,19]]
Output: 10
Explanation: Paint house 0 into blue, paint house 1 into green, paint house 2 into blue. 
             Minimum cost: 2 + 5 + 3 = 10.

Solution

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class Solution {
    public int minCost(int[][] costs) {
        if (costs == null || costs.length == 0 || costs[0].length == 0) return 0;
        
        int n = costs.length;
        int[][] dp = new int[costs.length][3];
        for (int i = 0; i < 3; i++)
            dp[0][i] = costs[0][i];
        
        for (int i = 1; i < n; i++){
            dp[i][0] = Math.min(dp[i - 1][1], dp[i - 1][2]) + costs[i][0];
            dp[i][1] = Math.min(dp[i - 1][0], dp[i - 1][2]) + costs[i][1];
            dp[i][2] = Math.min(dp[i - 1][0], dp[i - 1][1]) + costs[i][2];
        }
        
        return Math.min(dp[n - 1][0], Math.min(dp[n - 1][1], dp[n - 1][2]));
    }
}