[agc011F]Train Service Planning-[线段树优化dp+神秘思考题]

Description

传送门

Solution

请围观lhx大佬的博客（大佬写的太好了我都没有写的动力了em）

Code

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;
typedef long long ll;
int n,k;
int a[100010],b[100010];
ll sum[100010];
int L[100010],R[100010],t[200010];
ll dp[100010];

int tag[400010];
void downtag(int k)
{
    tag[k<<1]=tag[k<<1|1]=tag[k];
    tag[k]=0;
}
void modify(int k,int l,int r,int askx,int asky,int x)
{
    if (askx>asky) return;
    if (askx<=l&&r<=asky) {tag[k]=x;return;}
    int mid=(l+r)/2;
    if (tag[k]) downtag(k);
    if (askx<=mid) modify(k<<1,l,mid,askx,asky,x);
    if (mid<asky) modify(k<<1|1,mid+1,r,askx,asky,x);
}
int query(int k,int l,int r,int x)
{
    if (l==r) return tag[k];
    int mid=(l+r)/2;
    if (tag[k]) downtag(k);
    if (mid>=x) return query(k<<1,l,mid,x);
    else return query(k<<1|1,mid+1,r,x);
}
int cnt;
ll solve(int x){
    int re=query(1,1,cnt,x);
    if (!re) return 0;
    return dp[re]+((long long)t[L[re]]-t[x]+k)%k;
}
int main()
{
    scanf("%d%d",&n,&k);
    for (int i=1;i<=n;i++)
    {
        scanf("%d%d",&a[i],&b[i]);
        sum[i]=a[i]+sum[i-1];
        if (b[i]!=1) continue;
        if (2*a[i]>k) {puts("-1");return 0;}
    }
    for (int i=1;i<=n;i++)
    {
        if (b[i]==1)
        {
            L[i]=(-2*sum[i-1]%k+k)%k;
            R[i]=(-2*sum[i]%k+k)%k;
        }else L[i]=0,R[i]=k-1;
        t[i*2-1]=L[i],t[i*2]=R[i];
    }
    sort(t+1,t+2*n+1);
    cnt=unique(t+1,t+2*n+1)-t-1;
    for (int i=n;i;i--)
    {
        L[i]=lower_bound(t+1,t+cnt+1,L[i])-t;
        R[i]=lower_bound(t+1,t+cnt+1,R[i])-t;
        dp[i]=solve(L[i]);
        if (L[i]>R[i]) modify(1,1,cnt,R[i]+1,L[i]-1,i);
        else modify(1,1,cnt,1,L[i]-1,i),modify(1,1,cnt,R[i]+1,cnt,i);
    }
    ll ans=1e14;
    for (int i=1;i<=cnt;i++) ans=min(ans,solve(i));
    printf("%lld",ans+2*sum[n]);
}