class Solution {
public:
int maxProfit(vector<int>& prices) {
vector<vector<int> > dp(prices.size(), vector<int>(4, 0));
dp[0][0] = -prices[0];
dp[0][1] = 0;
dp[0][2] = 0;
dp[0][3] = 0;
for (int i = 1; i < prices.size(); i++) {
for (int j = 0; j <= 3; j++) {
dp[i][0] = max(dp[i - 1][0], max(dp[i - 1][1] - prices[i], dp[i - 1][3] - prices[i]));
dp[i][1] = max(dp[i - 1][1], dp[i - 1][3]);
dp[i][2] = dp[i - 1][0] + prices[i];
dp[i][3] = dp[i - 1][2];
}
}
return max(dp[prices.size() - 1][1], max(dp[prices.size() - 1][2], dp[prices.size() - 1][3]));
}
};
