LeetCode in Kotlin

188. Best Time to Buy and Sell Stock IV

Hard

You are given an integer array prices where prices[i] is the price of a given stock on the ith day, and an integer k.

Find the maximum profit you can achieve. You may complete at most k transactions.

Note: You may not engage in multiple transactions simultaneously (i.e., you must sell the stock before you buy again).

Example 1:

Input: k = 2, prices = [2,4,1]

Output: 2

Explanation: Buy on day 1 (price = 2) and sell on day 2 (price = 4), profit = 4-2 = 2.

Example 2:

Input: k = 2, prices = [3,2,6,5,0,3]

Output: 7

Explanation: Buy on day 2 (price = 2) and sell on day 3 (price = 6), profit = 6-2 = 4. Then buy on day 5 (price = 0) and sell on day 6 (price = 3), profit = 3-0 = 3.

Constraints:

• 1 <= k <= 100
• 1 <= prices.length <= 1000
• 0 <= prices[i] <= 1000

Solution

class Solution {
    fun maxProfit(k: Int, prices: IntArray): Int {
        val n = prices.size
        val dp = IntArray(k + 1)
        val maxdp = IntArray(k + 1)
        for (i in 0..k) {
            maxdp[i] = Int.MIN_VALUE
        }
        for (i in 1..n) {
            maxdp[0] = Math.max(maxdp[0], dp[0] - prices[i - 1])
            for (j in k downTo 1) {
                maxdp[j] = Math.max(maxdp[j], dp[j] - prices[i - 1])
                dp[j] = Math.max(maxdp[j - 1] + prices[i - 1], dp[j])
            }
        }
        return dp[k]
    }
}

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