题解 cf1155d 【beautiful array】

#define int long long
using namespace std;
inline int (){
    int x=0,w=0;char ch=getchar();
    while (!isdigit(ch))w|=ch=='-',ch=getchar();
    while (isdigit(ch))x=(x<<1)+(x<<3)+ch-'0',ch=getchar();
    return w?-x:x;
}
signed main(){
    int n=read(),m=read(),ans=0,a,f=0,g=0,h=0;
    for (int i=1;i<=n;++i)
        a=read(),h=max(h,max(g,0ll))+a,g=max(g,max(0ll,f))+a*m,f=max(f,0ll)+a,ans=max(ans,max(h,max(f,g)));
    cout<<ans;
    return 0;
}