LeetCode 309. Best Time to Buy and Sell Stock with Cooldown (DP)

題目

動態規劃
dp[i][0] 表示當天什麼都不操作
dp[i][1] 表示當天買進
dp[i][2] 表示當天賣出

狀態轉移就好寫出了

class Solution {
public:
    long long int dp[10005][3];
    int maxProfit(vector<int>& prices) {

        if (prices.size() == 0)
            return 0;
        dp[0][0] = 0;
        dp[0][1] = 0 - prices[0];
        dp[0][2] = INT32_MIN;
        for (int i = 1; i < prices.size(); i++)
        {
            dp[i][0] = INT32_MIN;
            dp[i][1] = INT32_MIN;
            dp[i][2] = INT32_MIN;
            for (int j = 0; j < i; j++)
            {
                if (dp[j][1] != INT32_MIN)
                {
                    dp[i][2] = max(dp[i][2], dp[j][1] + prices[i]);
                }
            }
            dp[i][0] = max(dp[i - 1][0], dp[i - 1][2]);
            dp[i][1] = dp[i - 1][0] - prices[i];

        }

        return max(dp[prices.size()-1][0], max(dp[prices.size()-1][1], dp[prices.size()-1][2]));
    
    }
    long long int max(long long int a, long long int b)
    {
        return a > b ? a : b;
    }
    
};