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# 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,** and you need to cost the least. Return the minimum cost.

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.

#### Example

**Example 1:**

```
Input: [[14,2,11],[11,14,5],[14,3,10]]
Output: 10
Explanation: Paint house 0 into blue, paint house 1 into green, paint house 2 into blue. Minimum cost: 2 + 5 + 3 = 10.
```

**Example 2:**

```
Input: [[1,2,3],[1,4,6]]
Output: 3
```

#### Notice

All costs are positive integers.

分析

从前一栋房子里另外几个颜色选最小

```
class Solution:
    """
    @param costs: n x 3 cost matrix
    @return: An integer, the minimum cost to paint all houses
    """
    def minCost(self, costs):
        # write your code here
        if not costs:
            return  0 
        n = len(costs)
        
        for i in range(1,n):
            costs[i][0] = costs[i][0] + min(costs[i-1][1],costs[i-1][2])
            costs[i][1] = costs[i][1] + min(costs[i-1][0],costs[i-1][2])
            costs[i][2] = costs[i][2] + min(costs[i-1][0],costs[i-1][1])
            
        return min(costs[n-1])

```