Submission #1241624

#	Time	Username	Problem	Language	Result	Execution time	Memory
1241624		Zero_OP	Safety (NOI18_safety)	C++17	100 / 100	35 ms	5216 KiB

safety

//CAUTION : this template is only suitable with C++17 (above) and home training, do not abuse when practicing offline
#include <bits/stdc++.h>

using namespace std;

//Benq inspires me lol
#define tcT template<class T
#define tcTU tcT, class U

//pairs
#define mp make_pair
#define mt make_tuple
#define ff first
#define ss second

//vectors
#define sz(v) (int)v.size()
#define all(v) begin(v), end(v)
#define rall(v) rbegin(v), rend(v)
#define pb push_back
#define eb emplace_back
#define compact(v) v.erase(unique(all(v)), end(v))

tcT> int lwb(const vector<T>& a, const T& b){ return int(lower_bound(all(a), b) - begin(a)); }
tcT> int upb(const vector<T>& a, const T& b){ return int(upper_bound(all(a), b) - begin(a)); }

//loops (warning : ONLY for int)
#define rep(i, l, r) for(int i = (l); i < (r); ++i)
#define FOR(i, l, r) for(int i = (l); i <= (r); ++i)

//debug
#define dbg(x) "[" #x " = " << (x) << "]"

//data types
using ll = long long;
using db = double;
using ld = long double;

using pi = pair<int, int>;
using pl = pair<ll, ll>;

using vi = vector<int>;
using vl = vector<ll>;
using vb = vector<bool>;
using vd = vector<db>;
using vc = vector<char>;
using vstr = vector<string>;

using vpi = vector<pi>;
using vpl = vector<pl>;

tcT> using min_heap = priority_queue<T, vector<T>, greater<T>>;
tcT> using max_heap = priority_queue<T>;

//bitwise operations
#define popcount(x) __builtin_popcountll(x) //count bits
#define BIT(k) (1LL << k) //bit k-th
#define all_bits(k) ((1LL << k) - 1) //first k bits on

//functions
tcT> bool minimize(T& a, const T& b){ if(a > b) return a = b, true; return false; } 
tcT> bool maximize(T& a, const T& b){ if(a < b) return a = b, true; return false; } 

tcT> T ceil_div(T a, T b){ return (a / b) + ((a ^ b) > 0 && a % b); }
tcT> T floor_div(T a, T b){ return (a / b) - ((a ^ b) < 0 && a % b); }

tcTU> T first_true(T lo, T hi, U f){ //if no exist then return hi+1
    ++hi; assert(lo <= hi); 
    while(lo < hi){ //[lo, hi)
        T mid = (lo + hi) >> 1;
        f(mid) ? hi = mid : lo = mid + 1;
    }
    return lo;
}

tcTU> T last_true(T lo, T hi, U f){ //if no exist then return lo-1
    --lo; assert(lo <= hi); 
    while(lo < hi){ //(lo, hi]
        T mid = (lo + hi) >> 1;
        f(mid) ? lo = mid : hi = mid - 1;
    }
    return lo;
}

tcT> void safe_erase(vector<T>& a, T x){
    auto it = find(all(a), x);
    if(it != a.end()) a.erase(it);
}

#ifdef LOCAL //for checking time elapsed
const auto start_time = std::chrono::high_resolution_clock::now();
db time_elapsed(){ return chrono::duration<db>(std::chrono::high_resolution_clock::now() - 
                                               start_time).count(); }
#endif //LOCAL

void setIO(){
    ios_base::sync_with_stdio(0); cin.tie(0);
#define task "task"
    if(fopen(task".inp", "r")){
        freopen(task".inp", "r", stdin);
        // freopen(task".out", "w", stdout);
    }
}

struct SlopeTrick{
    ll offset,  min_f, shift;
    max_heap<ll> L;
    min_heap<ll> R;

    SlopeTrick(ll H) : offset(0), shift(H), L(), R(), min_f(0) {}

    //add function |x - a| = max(0, x - a) + max(0, a - x)
    void add_abs_func(ll a){
        if(L.empty() && R.empty()){ //initial
            offset += shift; 
            L.push(a);
            R.push(a);
            return;
        }
        assert(!L.empty()); 
        assert(!R.empty());

        ll low = L.top() - offset, high = R.top() + offset; //optimum range [low, high]
        // cout << dbg(low) << dbg(high) << '\n';
        if(a < low){ //increase min_f
            // cout << "c\n";
            min_f += low - a;
            L.pop();
            R.push(low - offset);
            L.push(a + offset);
            L.push(a + offset);
            offset += shift;
        } else if(high < a){ //increase min_f
            // cout << "cc\n";
            min_f += a - high;
            R.pop();
            L.push(high + offset);
            R.push(a - offset);
            R.push(a - offset);
            offset += shift;
        } else{ //keep min_f
            // cout << "ccc\n";
            L.push(a + offset);
            R.push(a - offset);
            //apply shifting to make f_i(x) -> g_i(x)
            offset += shift;
        }
        // cout << dbg(min_f) << '\n';
    }   

    pl optimum(){
        assert(!L.empty() && !R.empty());
        return mp(L.top() - offset, R.top() + offset);
    }
    
    void output(){
        vl slopes;
        auto P = L;
        auto Q = R;
        while(!P.empty()){
            ll it = P.top(); P.pop();
            slopes.pb(it - offset);
        }

        while(!Q.empty()){
            ll it = Q.top(); Q.pop();
            slopes.pb(it + offset);
        }

        sort(all(slopes));
        for(auto it : slopes) cout << it << ' '; cout << '\n';
    }
};

void testcase(int n_case){
    int N, H;
    cin >> N >> H;
    vl a(N);
    rep(i, 0, N) cin >> a[i];

    SlopeTrick st(H);
    rep(i, 0, N){
        // cout << dbg(a[i]) << '\n';
        st.add_abs_func(a[i]);
        // auto [low, high] = st.optimum();
        // cout << low << ' ' << high << '\n';
        // st.output();
        // cout << '\n';
    }
    cout << st.min_f << '\n';
}

int main(){
    setIO();
    int T = 1; 
    // cin >> T;
    rep(i, 0, T) testcase(i);
#ifdef LOCAL
    cerr << '\n' << "Execution time : " << (time_elapsed() * 1000.0) << " ms";
#endif //LOCAL
    return 0;
}

Compilation message (stderr)

safety.cpp: In function 'void setIO()':
safety.cpp:100:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  100 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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