<JZOJ1329>旅行

贪心大水题

#include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>
#include<cmath>
#define rint register int
using std::max;
using std::min; 
template <class T>inline void read(T &X)
{
    X=0;int W=0;char ch=0;
    while(!isdigit(ch))W|=ch=='-',ch=getchar();
    while(isdigit(ch))X=(X<<3)+(X<<1)+(ch^48),ch=getchar();
    X=W?-X:X;return;
}
int n;
long long a[100010];
long long ans=0;
int main()
{
    read(n);
    for(rint i=1;i<=n;++i) read(a[i]);
    for(rint i=2;i<=n;++i)
    {
        int lst=a[i];
        if(a[i]>a[i+1] && a[i]>a[i-1])
            a[i]=max(a[i-1],a[i+1]),ans+=lst-a[i];
        if(a[i]<a[i+1] && a[i]<a[i-1])
            a[i]=min(a[i-1],a[i+1]),ans+=a[i]-lst;
    }
    for(rint i=2;i<=n;++i)
        ans+=abs(a[i]-a[i-1]);
    printf("%lld\n",ans);
return 0;
}