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

Say you have an array for which the ith element is the price of a given stock on day
i.

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;
}
}