Submission #527066

#	Time	Username	Problem	Language	Result	Execution time	Memory
527066		couplefire	Let's Win the Election (JOI22_ho_t3)	C++17	100 / 100	15 ms	2404 KiB

Main

#include <bits/stdc++.h>
using namespace std;
#define pii pair<int, int>
#define f first
#define s second

const int N = 505;
const int INF = 0x3f3f3f3f;

int n, k;
pii a[N];
double dp[N][N];

double s(int mid){
    for(int i = 1; i<=n; ++i)
        for(int j = 0; j<=i; ++j)
            dp[i][j] = min(dp[i-1][j]+(i-1-j>=mid?0:(.0+a[i].s)/(.0+i-j)), (j>=1?dp[i-1][j-1]+(.0+a[i].f)/(.0+mid+1):INF));
    double ans = INF;
    for(int i = k-mid; i<=n; ++i)
        if(n-i>=mid) ans = min(ans, dp[n][i]);
    return ans;
}

int main(){
    cin.tie(0)->sync_with_stdio(0);
    cout << setprecision(12) << fixed;
    cin >> n >> k;
    for(int i = 1; i<=n; ++i)
        cin >> a[i].f >> a[i].s;
    int mx = 0;
    for(int i = 1; i<=n; ++i)
        if(a[i].s==-1) a[i].s = INF;
        else ++mx;
    sort(a+1, a+1+n, [&](pii a, pii b){return a.s<b.s;});
    int lo = 0, hi = min(k, mx);
    while(lo<hi){
        int mid = (lo+hi)>>1;
        if(s(mid)<=s(mid+1)) hi = mid;
        else lo = mid+1;
    } cout << s(lo) << '\n';
}

• Subtask 1: 5 / 5
• Subtask 2: 5 / 5
• Subtask 3: 11 / 11
• Subtask 4: 12 / 12
• Subtask 5: 33 / 33
• Subtask 6: 11 / 11
• Subtask 7: 23 / 23