BZOJ1911【斜率优化】

/* I will wait for you */ #include<cstdio>#include<cstdlib>#include<cstring>#include<cmath>#include<ctime>#include<algorithm>#include<iostream>#include<fstream>#include<vector>#include<queue>#include<deque>#include<set>#include<map>#include<string>#define make(a,b) make_pair(a,b)#define fi first#define se second using namespace std; typedef long long LL;typedef unsigned long long ULL;typedef pair<int,int> PII; const int maxn=1000010;const int maxm=1000010;const int maxs=26;const int INF=1<<29;const int P=1000000007;const double error=1e-9;LL a,b,c,x[maxn],q[maxn],f[maxn],h[maxn],s[maxn];LL F(LL x){return a*x*x+b*x+c;}LL A(int x,int y){return (h[x]-f[x]+2*a*s[x]*s[x])-(h[y]-f[y]+2*a*s[y]*s[y]);}LL B(int x,int y){return (2*a*s[x])-(2*a*s[y]);}int main(){int n;scanf("%d%lld%lld%lld",&n,&a,&b,&c);for(int i=1;i<=n;i++) scanf("%lld",&x[i]);for(int i=1;i<=n;i++) s[i]=s[i-1]+(LL)x[i],f[i]=F(s[i]);int he=0,ta=0;f[0]=c;for(int i=1,t;i<=n;i++){while(he<ta&&A(q[he],q[he+1])<=B(q[he],q[he+1])*s[i]) he++;t=q[he],h[i]=h[t]+F(s[i]-s[t]);while(he<ta&&A(q[ta-1],q[ta])*B(q[ta],i)>=A(q[ta],i)*B(q[ta-1],q[ta])) ta--;q[++ta]=i;}printf("%lld\n",h[n]);return 0;}