Submission #1081576

#	Time	Username	Problem	Language	Result	Execution time	Memory
1081576		Icelast	Group Photo (JOI21_ho_t3)	C++17	100 / 100	403 ms	604 KiB

Main

#include <iostream>
#include <bits/stdc++.h>
#define ll long long
using namespace std;
const ll maxn = 5005, INF = 1e9+9;
struct BIT{
    int n;
    vector<int> bit;
    BIT(int n) : n(n){
        bit.resize(n+1, 0);
    };
    void upd(int i, int x){
        while(i <= n){
            bit[i] += x;
            i += i&-i;
        }
    }
    int sum(int l, int r){
        int res = 0;
        l--;
        while(l > 0){
            res -= bit[l];
            l-=l&-l;
        }
        while(r > 0){
            res += bit[r];
            r-=r&-r;
        }
        return res;
    }
};
void solve(){
    int n;
    cin >> n;
    vector<int> a(n+1), p(n+1);
    for(int i = 1; i <= n; i++){
        cin >> a[i];
        p[a[i]] = i;
    }
    vector<int> dp(n+1, INF);
    dp[0] = 0;
    BIT bit(n+1), bit2(n+1);
    int d;
    for(int i = 1; i <= n; i++){
        d = 0;
        bit.upd(p[i], 1);
        for(int j = 1; j <= i; j++){
            bit.upd(p[i-j+1], -1);
            d += p[i-j+1]-1-bit.sum(1, p[i-j+1])-bit2.sum(1, p[i-j+1]);
            d += bit2.sum(p[i-j+1], n);
            dp[i] = min(dp[i], dp[i-j]+d);
            bit2.upd(p[i-j+1], 1);
        }
        swap(bit, bit2);
    }
    cout << dp[n];
}
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    solve();
}

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