Submission #1309490

#	Time	Username	Problem	Language	Result	Execution time	Memory
1309490		tnt	Lightning Rod (NOI18_lightningrod)	C++20	19 / 100	1033 ms	131848 KiB

Main

#include <bits/stdc++.h>
using namespace std;
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
//#pragma GCC optimize("Ofast,unroll-loops,fast-math,O3")

#define pb push_back                    
#define ll long long  
#define f first
#define s second
//#define sz(v) int(v.size())
#define all(v) v.begin(),v.end()

int mod =  1e9 + 7;
const int N = 2e5,k = 317 + 1;
const int inf = 2e9;
void solve(){
    int n;
    cin >> n;
    vector <pair<int,int>> v;
    int cnt = 0,cnt1 = 0;
    for(int i = 1; i <= n; i++){
        int x,y;
        cin >> x >> y;
        if(x == i) cnt1++;
        if(y == 1) cnt++;
        v.pb({x,y});
    }
    if(cnt == n){
        cout << n;
        return;
    }
    if(cnt1 == n){
        int ans = 0;
        for(int i = 0; i < v.size(); i++){
            if(v[i].s == 1){
                ans++;
                if(i - 1 >= 0 && v[i - 1].s == 0){
                    v[i - 1].s = -1;   
                }
                if(i + 1 < n && v[i + 1].s == 0){
                    v[i + 1].s = -1;   
                }
                v[i].s = -1;
            }
        }
        for(int i = 0; i < v.size(); i++) if(v[i].s != -1) ans++;
        cout << ans << '\n';
        return;
    }
    if(n <= 20){
        int ans = inf;
        for(int mask = 0; mask < (1 << n); mask++){
            vector <int> v1;
            for(int i = 0; i < n; i++){
                if((mask >> i & 1) == 1){
                    v1.pb(i);
                }
            }
            bool f1 = 1;
            for(int i = 0; i < n; i++){
                int x,y;
                bool f = 0;
                for(auto to : v1){
                    x = v[to].f,y = v[to].s;
                    if(abs(x - v[i].f) <= y - v[i].s){
                        f = 1;
                        break;
                    }
                }
                if(f == 0){
                    f1 = 0;
                }
            }
            if(f1 == 1){
                ans = min(ans,__builtin_popcount(mask));
            }
        }
        cout << ans;
    }
}
signed main(){
    //freopen("time.in", "r", stdin);
    //freopen("time.out", "w", stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    int t = 1;
    while(t--){
        solve();
    }
}                          	

• Subtask 1: 0 / 4
• Subtask 2: 7 / 7
• Subtask 3: 12 / 12
• Subtask 4: 0 / 21
• Subtask 5: 0 / 26
• Subtask 6: 0 / 10
• Subtask 7: 0 / 20