【noi 2.6_8464】股票买卖（DP）

 1 #include<cstdio>
 2 #include<cstdlib>
 3 #include<cstring>
 4 #include<iostream>
 5 using namespace std;
 6 
 7 #define N 100010
 8 #define INF 1000010
 9 int a[N],f[N],g[N];
10 int mmin(int x,int y) {return x<y?x:y;}
11 int mmax(int x,int y) {return x>y?x:y;}
12 
13 int main()
14 {
15     int T,n;
16     scanf("%d",&T);
17     while (T--)
18     {
19       scanf("%d",&n);
20       int ans=0,mn=INF,mx=-INF;
21       f[0]=g[n+1]=-INF;
22       for (int i=1;i<=n;i++)
23       {
24         scanf("%d",&a[i]);
25         mn=mmin(mn,a[i]);
26         f[i]=mmax(f[i-1],a[i]-mn);
27       }
28       for (int i=n;i>=1;i--)
29       {
30         mx=mmax(mx,a[i]);
31         g[i]=mmax(g[i+1],-a[i]+mx);
32         ans=mmax(ans,f[i]+g[i]);
33       }
34       printf("%d\n",ans);
35     }
36     return 0;
37 }