Submission #130107

#	Time	Username	Problem	Language	Result	Execution time	Memory
130107		Utaha	Sparklers (JOI17_sparklers)	C++14	100 / 100	36 ms	2984 KiB

sparklers

/*input
3 2 10
0
200
300
*/
#include <bits/stdc++.h>
#pragma GCC optimize("unroll-loops,no-stack-protector")
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef pair<ld,ld> pdd;
#define IOS ios_base::sync_with_stdio(0); cin.tie(0)
#define ALL(a) a.begin(),a.end()
#define SZ(a) ((int)a.size())
#define F first
#define S second
#define REP(i,n) for(int i=0;i<((int)n);i++)
#define pb emplace_back
#define MP(a,b) make_pair(a,b)
#define SORT_UNIQUE(c) (sort(c.begin(),c.end()), c.resize(distance(c.begin(),unique(c.begin(),c.end()))))
#define GET_POS(c,x) (lower_bound(c.begin(),c.end(),x)-c.begin())
template<typename T1,typename T2>
ostream& operator<<(ostream& out,pair<T1,T2> P){
    out<<'('<<P.F<<','<<P.S<<')';
    return out;
}
 
//}}}
const ll maxn=100005;
const ll maxlg=__lg(maxn)+2;
const ll INF64=8000000000000000000LL;
const int INF=0x3f3f3f3f;
const ll MOD=ll(1e9+7);
const ld PI=acos(-1);
const ld eps=1e-9;
//const ll p=880301;
//const ll P=31;
 
ll mypow(ll a,ll b){
    ll res=1LL;
    while(b){
        if(b&1) res=res*a%MOD;
        a=a*a%MOD;
        
        b>>=1;
    }
    return res;
}
int n,k;
ll t;
ll a[maxn];
ll x[maxn];

bool check(ll s){
    REP(i,n) x[i]=a[i]-2*t*s*i;
    if(x[0]<x[n-1]) return 0;
    int gl=max_element(x,x+k+1)-x;
    int gr=min_element(x+k,x+n)-x;

    {
        int l=k,r=k;
        while(l!=gl||r!=gr){
            int nxt=l;
            bool f=0;
            while(nxt>gl&&x[nxt-1]>=x[r]){
                nxt--;
                if(x[nxt]>=x[l]){
                    f=1;
                    break;
                }
            }
            if(f){
                l=nxt;
                continue;
            }
            nxt=r;
            while(nxt<gr&&x[nxt+1]<=x[l]){
                nxt++;
                if(x[nxt]<=x[r]){
                    f=1;
                    break;
                }
            }
            if(f){
                r=nxt;
                continue;
            }
            break;
        }
        if(l!=gl||r!=gr) return 0;
    }
    {
        int l=0,r=n-1;
        while(l!=gl||r!=gr){
            int nxt=l;
            bool f=0;
            while(nxt<gl&&x[nxt+1]>=x[r]){
                nxt++;
                if(x[nxt]>=x[l]){
                    f=1;
                    break;
                }
            }
            if(f){
                l=nxt;
                continue;
            }
            nxt=r;
            while(nxt>gr&&x[nxt-1]<=x[l]){
                nxt--;
                if(x[nxt]<=x[r]){
                    f=1;
                    break;
                }
            }
            if(f){
                r=nxt;
                continue;
            }
            break;
        }
        if(l!=gl||r!=gr) return 0;
    }
    return 1;
}
 
int main(){
    IOS;
    cin>>n>>k>>t;
    k--;
    REP(i,n) cin>>a[i];
    ll l=-1,r=1000000000LL;
    while(l!=r-1){
        ll mid=(l+r)/2;
        if(check(mid)) r=mid;
        else l=mid;
    }
    cout<<r<<'\n';
    return 0;
}

• Subtask 1: 30 / 30
• Subtask 2: 20 / 20
• Subtask 3: 50 / 50