初学斜率优化……
#include<cstdio> #include<cstring> #include<algorithm> using namespace std; #define maxn 500005 int sum[maxn]; int dp[maxn]; int a[maxn]; int q[maxn]; int y(int i) { return dp[i]+sum[i]*sum[i]; } int Gup(int j,int k) { return y(j)-y(k); } int Gdown(int j,int k) { return sum[j]-sum[k]; } inline int ReadInt() //开挂,刷一下排行 { char ch = getchar(); int data = 0; while (ch < '0' || ch > '9') { ch = getchar(); } do { data = data*10 + ch-'0'; ch = getchar(); }while (ch >= '0' && ch <= '9'); return data; } int main() { int n,m; while(scanf("%d%d",&n,&m)!=EOF) { sum[0]=0; for(int i=1;i<=n;i++){ a[i]=ReadInt(); sum[i]=sum[i-1]+a[i]; } int head=0,tail=-1; q[++tail]=0; for(int i=1;i<=n;i++) { while(head<tail&&Gup(q[head+1],q[head])<=2*sum[i]*Gdown(q[head+1],q[head])) head++; dp[i]=dp[q[head]]+(sum[i]-sum[q[head]])*(sum[i]-sum[q[head]])+m; while(head<tail&&Gup(i,q[tail])*Gdown(q[tail],q[tail-1])<=Gup(q[tail],q[tail-1])*Gdown(i,q[tail])) tail--; q[++tail]=i; } printf("%d\n",dp[n]); } return 0; }