LeetCode "Paint House"

class Solution {
public:
int minCost(vector<vector<int>>& costs) {
size_t len = costs.size();
if(len == 0) return 0;

vector<vector<int>> dp(len, vector<int>(3, 0));
dp[0] = costs[0];
for(int i = 1; i < len; i ++)
{
for(int c = 0; c < 3; c ++)
{
unordered_set<int> cand = {0, 1, 2};
cand.erase(c);
auto it = cand.begin();
int a = *it ++, b = *it;

dp[i][c] = costs[i][c] + std::min(dp[i - 1][a], dp[i - 1][b]);
}
}
return *std::min_element(dp[len - 1].begin(), dp[len - 1].end());
}
};