LeetCode 123 Best Time to Buy and Sell Stock III (贪心)

Say you have an array for which the i^th element is the price of a given stock on dayi.

Design an algorithm to find the maximum profit. You may complete at most two transactions.

Note:
You may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).

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

题目分析：与Best Time to Buy and Sell Stock类似，这题可以交易两次，容易想到分别从前往后，从后往前找到当前的最大值，然后枚举分割点

public class Solution {    public int maxProfit(int[] prices) {        int len = prices.length;        if (len == 0) {            return 0;        }        int[] left = new int[len];        int[] right = new int[len];        int lMin = prices[0], rMax = prices[len - 1];        for (int i = 1; i < len; i ++) {            if (prices[i] < lMin) {                lMin = prices[i];                left[i] = left[i - 1];            }            else {                left[i] = Math.max(left[i - 1], prices[i] - lMin);            }        }        for (int i = len - 2; i >= 0; i --) {            if (prices[i] > rMax) {                rMax = prices[i];                right[i] = right[i + 1];            }            else {                right[i] = Math.max(right[i + 1], rMax - prices[i]);            }        }        int ans = 0;        for (int i = 0; i < len; i ++) {            ans = Math.max(ans, left[i] + right[i]);        }        return ans;     }}