动态规划_百炼 4121 股票买卖

 1 #define _CRT_SECURE_NO_WARNINGS  
 2 #include <stdio.h>
 3 #include <math.h>
 4 #include <algorithm>
 5 #include <stdlib.h>
 6 #include <vector>
 7 #include <map>
 8 #include <queue>
 9 #include <string>
10 #include <iostream>
11 #include <ctype.h>
12 #include <string.h>
13 #include <set>
14 #include <stack>
15 #include<functional>
16 using namespace std;
17 #define size 100001
18 #define maxn  1<<30
19 int past[size];//past[i]表示在第i天之后(包括i)买入,在第i天后面的某天卖出所能赚到的最大钱数
20 int pre[size];//pre[i]表示在第i天之前(包括i)卖出,在第i天之前买入所能获得的最大利润
21 int a[size];
22 /*
23 
24 
25 */
26 int main(){
27     int T;
28     cin >> T;
29     while (T--){
30         int n;
31         cin >> n;
32         memset(past, 0, sizeof(past));
33         memset(pre, 0, sizeof(pre));
34         for (int i = 1; i <= n; i++)
35             scanf("%d", &a[i]);
36         int low_prise = a[1];//买入的价格
37         pre[1] = 0;
38         for (int i = 2; i <= n; i++)
39         {
40             low_prise = min(low_prise, a[i]);
41             pre[i] = max(pre[i-1],a[i] - low_prise);//如果等于0 表示今天买入今天卖出
42         }
43         int high_prise = a[n];//卖出的价格
44         past[n] = 0;
45         for (int i = n - 1; i >= 1; i--)
46         {
47             high_prise = max(high_prise, a[i]);
48             past[i] = max(past[i+1],high_prise - a[i]);
49         }
50         int max_profit = 0;
51         for (int i = 1; i <= n; i++)
52             max_profit = max(max_profit, past[i] + pre[i]);
53         cout << max_profit << endl;
54     }
55     system("pause");
56     return 0;
57 }