The 1st row is the prices for the 1st house, we can change the matrix to present sum of prices from the 2nd row. i.e, the costs[1][0] represent minimum price to paint the second house red plus the 1st house.

```
public 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]);
}
```

}