luoguP2365 任务安排 斜率优化 + 动态规划

Code: 

#include<bits/stdc++.h>
#define setIO(s) freopen(s".in","r",stdin) 
#define ll long long 
#define x(i) (sumf[i]) 
#define y(i) (f[i]) 
#define maxn 1000000 
using namespace std; 
int n,s,head,tail;
int q[maxn];  
ll sumt[maxn],sumf[maxn],f[maxn];   
double slope(int i,int j) { return (double)(1.00*(y(i)-y(j)))/(double)(1.00*(x(i)-x(j)));}
int main()
{ 
    // setIO("input"); 
    int i,j; 
    scanf("%d%d",&n,&s); 
    for(i=1;i<=n;++i) 
    {
        scanf("%lld%lld",&sumt[i],&sumf[i]); 
        sumt[i]+=sumt[i-1],sumf[i]+=sumf[i-1]; 
    }
    head=tail=0; 
    for(i=1;i<=n;++i) 
    {
        while(head<tail&&slope(q[head],q[head+1])<=sumt[i]+s)++head; 
        f[i]=y(q[head])+sumf[i]*sumt[i]+s*sumf[n]-(sumt[i]+s)*x(q[head]);    
        while(head<tail&&slope(q[tail],i)<slope(q[tail-1],i)) --tail; 
        q[++tail]=i; 
    }
    printf("%lld
",f[n]); 
    return 0; 
}