习题-[SCOI2009]生日礼物(双指针)

习题-[SCOI2009]生日礼物

#include <bits/stdc++.h>
using namespace std;

typedef pair<int, int> PII;

bool vis[1000010];
unordered_map<int, int> mp;

signed main(){
    int n, k; cin >> n >> k;
    vector<PII> p;
    
    for(int i = 1; i <= k; ++i){
        int t; cin >> t;
        for(int j = 1; j <= t; ++j){
            int x; cin >> x;
            p.push_back({x, i});
        }
    }
    sort(p.begin(), p.end());
    
    long long res = 1e9;
    long long l = 0, r = 0;
    int cnt = 0;
    while(r < n){
        if(!mp[p[r].second]) ++cnt;
        mp[p[r].second]++;
        while(cnt == k && mp[p[l].second] > 1){
            mp[p[l].second]--;
            if(!mp[p[l].second]) --cnt;
            ++l;
            res = min(res, p[r].first - p[l].first - 0ll);
        }
        ++r;
    }
    cout << res << endl;
    
    return 0;
}