309. the best time to buy and sell stocks includes the freezing period

Preface

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describe

Given an array of integers prices, Among them the first   prices[i] It means the first one i Day's share price .​

Design an algorithm to calculate the maximum profit . Under the following constraints , You can do as many deals as you can （ Buy and sell a stock many times ）:

    After sale of shares , You can't buy shares the next day ( That is, the freezing period is 1 God ).

Be careful ： You can't participate in multiple transactions at the same time （ You have to sell the stock before you buy it again ）.

Example 1:

Input : prices = [1,2,3,0,2]
Output : 3
explain : The corresponding transaction status is : [ purchase , sell , Freezing period , purchase , sell ]

Example 2:

Input : prices = [1]
Output : 0

class Solution {
    public int maxProfit(int[] prices) {
        if (prices.length == 0) {
            return 0;
        }

        int n = prices.length;
        // f[i][0]:  The biggest return on the stock you hold 
        // f[i][1]:  I don't have stock in my hand , And it's in the middle of the freezing period 
        // f[i][2]:  I don't have stock in my hand , And the cumulative maximum return not in the freezing period 
        int[][] f = new int[n][3];
        f[0][0] = -prices[0];
        for (int i = 1; i < n; ++i) {
            f[i][0] = Math.max(f[i - 1][0], f[i - 1][2] - prices[i]);
            f[i][1] = f[i - 1][0] + prices[i];
            f[i][2] = Math.max(f[i - 1][1], f[i - 1][2]);
        }
        return Math.max(f[n - 1][1], f[n - 1][2]);
    }
}