Best Time to Buy and Sell Stock III.cpp

// https://leetcode.com/problems/best-time-to-buy-and-sell-stock-iii/

class Solution {
public:
    int maxProfit(vector<int>& prices) {
        int states[2][4] = {INT_MIN, 0, INT_MIN, 0}; // 0: 1 buy, 1: one buy/sell, 2: 2 buys/1 sell, 3, 2 buys/sells
        int len = prices.size(), i, cur = 0, next =1;
        for(i=0; i<len; ++i)
        {
            states[next][0] = max(states[cur][0], -prices[i]);
            states[next][1] = max(states[cur][1], states[cur][0]+prices[i]);
            states[next][2] = max(states[cur][2], states[cur][1]-prices[i]);
            states[next][3] = max(states[cur][3], states[cur][2]+prices[i]);
            swap(next, cur);
        }
        return max(states[cur][1], states[cur][3]);
    }
};