题目：

题解：

class Solution {
public:int maxProfit(int k, vector<int>& prices) {if (prices.empty()) {return 0;}int n = prices.size();k = min(k, n / 2);vector<int> buy(k + 1);vector<int> sell(k + 1);buy[0] = -prices[0];sell[0] = 0;for (int i = 1; i <= k; ++i) {buy[i] = sell[i] = INT_MIN / 2;}for (int i = 1; i < n; ++i) {buy[0] = max(buy[0], sell[0] - prices[i]);for (int j = 1; j <= k; ++j) {buy[j] = max(buy[j], sell[j] - prices[i]);sell[j] = max(sell[j], buy[j - 1] + prices[i]);   }}return *max_element(sell.begin(), sell.end());}
};