cf1358E. Are You Fired?

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题解

如果长度为 $k$的可以，那么 $2k$肯定也可以，所以如果答案存在的话肯定存在一个不小于 $\lceil \frac{n}{2} \rceil$的答案

代码

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define iinf 0x3f3f3f3f
#define linf (1ll<<60)
#define eps 1e-8
#define maxn 1000010
#define maxe 1000010
#define cl(x) memset(x,0,sizeof(x))
#define rep(i,a,b) for(i=a;i<=b;i++)
#define drep(i,a,b) for(i=a;i>=b;i--)
#define em(x) emplace(x)
#define emb(x) emplace_back(x)
#define emf(x) emplace_front(x)
#define fi first
#define se second
#define de(x) cerr<<#x<<" = "<<x<<endl
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
ll read(ll x=0)
{
    ll c, f(1);
    for(c=getchar();!isdigit(c);c=getchar())if(c=='-')f=-f;
    for(;isdigit(c);c=getchar())x=x*10+c-0x30;
    return f*x;
}
struct SegmentTree
{
    ll mn[maxn<<2], mx[maxn<<2], sum[maxn<<2], add[maxn<<2], set[maxn<<2], L[maxn<<2], R[maxn<<2];
    void maketag_set(ll o, ll v)
    {
        add[o]=0;
        set[o]=v;
        mx[o]=mn[o]=v;
        sum[o]=(R[o]-L[o]+1)*v;
    }
    void maketag_add(ll o, ll v)
    {
        add[o]+=v;
        mx[o]+=v, mn[o]+=v;
        sum[o]+=(R[o]-L[o]+1)*v;
    }
    void pushdown(ll o)
    {
        if(L[o]==R[o])return;
        if(~set[o])
        {
            maketag_set(o<<1,set[o]);
            maketag_set(o<<1|1,set[o]);
            set[o]=-1;
        }
        if(add[o])
        {
            maketag_add(o<<1,add[o]);
            maketag_add(o<<1|1,add[o]);
            add[o]=0;
        }
    }
    void pushup(ll o)
    {
        mx[o]=max(mx[o<<1],mx[o<<1|1]);
        mn[o]=min(mn[o<<1],mn[o<<1|1]);
        sum[o]=sum[o<<1]+sum[o<<1|1];
    }
    void build(ll o, ll l, ll r, ll* array=NULL)
    {
        ll mid(l+r>>1);
        L[o]=l, R[o]=r;
        add[o]=0;
        set[o]=-1;
        if(l==r)
        {
            if(array)mn[o]=mx[o]=sum[o]=array[l];
            else mn[o]=mx[o]=sum[o]=0;
            return;
        }
        build(o<<1,l,mid,array);
        build(o<<1|1,mid+1,r,array);
        pushup(o);
    }
    void Set(ll o, ll l, ll r, ll v)
    {
        ll mid(L[o]+R[o]>>1);
        if(l<=L[o] and r>=R[o]){maketag_set(o,v);return;}
        pushdown(o);
        if(l<=mid)Set(o<<1,l,r,v);
        if(r>mid)Set(o<<1|1,l,r,v);
        pushup(o);
    }
    void Add(ll o, ll l, ll r, ll v)
    {
        ll mid(L[o]+R[o]>>1);
        if(l<=L[o] and r>=R[o]){maketag_add(o,v);return;}
        pushdown(o);
        if(l<=mid)Add(o<<1,l,r,v);
        if(r>mid)Add(o<<1|1,l,r,v);
        pushup(o);
    }
    ll Sum(ll o, ll l, ll r)
    {
        pushdown(o);
        ll mid(L[o]+R[o]>>1), ans(0);
        if(l<=L[o] and r>=R[o])return sum[o];
        if(l<=mid)ans+=Sum(o<<1,l,r);
        if(r>mid)ans+=Sum(o<<1|1,l,r);
        return ans;
    }
    ll Min(ll o, ll l, ll r)
    {
        ll mid(L[o]+R[o]>>1), ans(linf);
        if(l<=L[o] and r>=R[o])return mn[o];
        pushdown(o);
        if(l<=mid)ans=min(ans,Min(o<<1,l,r));
        if(r>mid)ans=min(ans,Min(o<<1|1,l,r));
        return ans;
    }
    ll Max(ll o, ll l, ll r)
    {
        ll mid(L[o]+R[o]>>1), ans(-linf);
        if(l<=L[o] and r>=R[o])return mx[o];
        pushdown(o);
        if(l<=mid)ans=max(ans,Max(o<<1,l,r));
        if(r>mid)ans=max(ans,Max(o<<1|1,l,r));
        return ans;
    }
}segtree;
ll a[maxn], s[maxn], k;
int main()
{
    ll i, n=read(), x;
    rep(i,1,(n+1)>>1)a[i]=read(), s[i]=s[i-1]+a[i];
    x=read();
    rep(i,(n+1>>1)+1,n)a[i]=x, s[i]=s[i-1]+a[i];
    k = (n+1>>1);
    rep(i,1,n-k+1)a[i]=s[i+k-1]-s[i-1];
    segtree.build(1,1,n-k+1,a);
    rep(k,(n+1>>1),n)
    {
        ll t = segtree.Min(1,1,n-k+1);
        if(t>0)
        {
            printf("%lld",k);
            return 0;
        }
        segtree.Add(1,1,n-k,+x);
    }
    printf("-1");
    return 0;
}