README.md

188. Best Time to Buy and Sell Stock IV

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: i.e. you may buy at most k times and sell at most k times.

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

Solutions (Rust)

1. Solution

impl Solution {
    pub fn max_profit(k: i32, prices: Vec<i32>) -> i32 {
        let k = k as usize;
        let mut dp = vec![[0, i32::MIN]; k + 1];
        let mut ret = 0;

        for i in 0..prices.len() {
            let mut tmp = dp.clone();

            for j in 0..=i.min(k) {
                if j < k {
                    tmp[j + 1][1] = tmp[j + 1][1].max(dp[j][0] - prices[i]);
                }
                tmp[j][0] = tmp[j][0].max(dp[j][1] + prices[i]);
                ret = ret.max(tmp[j][0]);
            }

            dp = tmp;
        }

        ret
    }
}