23.02.27 学习

状态机分析法很牛逼，看图吧

class Solution {
public:
    int maxProfit(vector<int>& prices) {
        if (prices.empty()) return 0;
        int n = prices.size();
        vector<vector<int>> f(n, vector<int>(3));

        f[0][0] = 0, f[0][1] = -prices[0];
        for (int i = 1; i < n; i ++ ) {
            f[i][0] = max(f[i - 1][0], f[i - 1][2]);
            f[i][1] = max(f[i - 1][0] - prices[i], f[i - 1][1]);
            f[i][2] = f[i - 1][1] + prices[i];
        }

        return max(f[n - 1][0], max(f[n - 1][1], f[n - 1][2]));
    }
};