CF788A Functions again dp

求一个最长子段和就完了，可以出T1?

code:

#include <bits/stdc++.h>
#define N 100006
#define ll long long
#define setIO(s) freopen(s".in","r",stdin)
using namespace std;
ll a[N],A[N],B[N],f[N],g[N];
int main()
{
    ll mx=0;
    int i,j,n;
    // setIO("input");
    scanf("%d",&n);
    for(i=1;i<=n;++i) scanf("%lld",&a[i]);
    for(i=1;i<n;++i)
    {
        if(i%2==1) A[i]=abs(a[i]-a[i+1]), B[i]=-A[i];
        else A[i]=-abs(a[i]-a[i+1]), B[i]=-A[i];
    }
    f[1]=A[1], g[1]=B[1];
    mx=max(A[1], B[1]);
    for(i=2;i<n;++i)
    {
        f[i]=max(f[i-1],0*1ll)+A[i];
        g[i]=max(g[i-1],0*1ll)+B[i];
        mx=max(mx, f[i]);
        mx=max(mx, g[i]);
    }
    printf("%lld\n",mx);
    return 0;
}