LeetCode 123. Best Time to Buy and Sell Stock III (stock problem)
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).
分析
首先不压缩空间的写法,写法依然参照stock problem精帖的base case ,分别用一个二维数组去储存sell和buy的状况
const int inf=-999999;
class Solution {
public:
int maxProfit(vector<int>& prices) {
if(prices.size()<=1)
return 0;
int days=prices.size();
int sell[days+1][3],buy[days+1][3];
for(int i=0;i<3;i++){
sell[0][i]=0;
buy[0][i]=inf;
}
for(int i=0;i<=prices.size();i++){
sell[i][0]=0;
buy[i][0]=inf;
}
for(int i=1;i<=prices.size();i++){
for(int k=1;k<=2;k++){
sell[i][k]=max(sell[i-1][k],buy[i-1][k]+prices[i-1]);
buy[i][k]=max(buy[i-1][k],sell[i-1][k-1]-prices[i-1]);
}
}
return sell[prices.size()][2];
}
};