188.best-time-to-buy-and-sell-stock-iv.java

/*
 * @lc app=leetcode id=188 lang=java
 *
 * [188] Best Time to Buy and Sell Stock IV
 */

// @lc code=start
class Solution {
    public int maxProfit(int k, int[] prices) {
        int n = prices.length;
        if (n == 0) {
            return 0;
        }
        if (k > n / 2) {
            return maxProfit_caseII(prices);
        }
        
        int[][][] dp = new int[n][k + 1][2];

        for (int i = 0; i < prices.length; i++) {
            for (int j = k; j >= 1; j--) {
                if (i - 1 == -1) {
                    dp[i][j][0] = 0;
                    dp[i][j][1] = -prices[i];
                    continue;
                }
                dp[i][j][0] = Math.max(dp[i - 1][j][0], dp[i - 1][j][1] + prices[i]);
                dp[i][j][1] = Math.max(dp[i - 1][j][1], dp[i - 1][j - 1][0] - prices[i]);
            }
        }
        
        return dp[n - 1][k][0];
    }

    public int maxProfit_caseII(int[] prices) {
        int dp_i_0 = 0;
        int dp_i_1 = Integer.MIN_VALUE;

        for (int i = 0; i < prices.length; i++) {
            int temp = dp_i_0;
            dp_i_0 = Math.max(dp_i_0, dp_i_1 + prices[i]);
            dp_i_1 = Math.max(dp_i_1, temp - prices[i]);
        }
        return dp_i_0;
    }
}
// @lc code=end