Submission #380386

#	Time	Username	Problem	Language	Result	Execution time	Memory
380386		nvmdava	Group Photo (JOI21_ho_t3)	C++17	100 / 100	577 ms	67692 KiB

Main

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ff first
#define ss second
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int N = 500'005;
const ll MOD = 1'000'000'007;
const ll INF = 0x3f3f3f3f3f3f3f3f;

int a[5005][5005];
int bit[5005];

int h[N];
int loc[N];

void update(int x){
    while(x < 5005){
        ++bit[x];
        x += x & -x;
    }
}

int get(int x){
    int s = 0;
    while(x){
        s += bit[x];
        x -= x & -x;
    }
    return s;
}

int dp[5005];

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    int n;
    cin>>n;

    for(int i = 1; i <= n; ++i){
        cin>>h[i];
        loc[h[i]] = i;
    }

    for(int i = 1; i <= n; ++i){
        for(int j = 0; j < 5005; ++j)
            bit[j] = 0;
        for(int j = i; j <= n; ++j){
            a[i][j] = a[i][j - 1] + j - i - get(loc[j]);
            update(loc[j]);
        }
    }

    for(int i = 0; i <= n; ++i){
        dp[i] = a[1][n];
        for(int j = 0; j < i; ++j)
            dp[i] = min(dp[i], dp[j] - a[j + 1][i] + (i - j) * (i - j - 1) / 2 - a[j + 1][i]);
    }
    cout<<dp[n];
}

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 32 / 32
• Subtask 4: 20 / 20
• Subtask 5: 36 / 36