Codeforces 1090C New Year Presents

#include<bits/stdc++.h>
#define LL long long
#define fi first
#define se second
#define mk make_pair
#define PII pair<int, int>
using namespace std;

const int N = (int)1e5 + 7;

int n, m, sum, min_cnt, tar[N], num[N], vis[N];
bool ban[N], gg[N];
vector<int> V[N], P[N], T[N];
set<int> S;
vector<pair<PII, int>> ans;

int main() {
    scanf("%d%d", &n, &m);
    for(int i = 1; i <= n; i++) {
        int s; scanf("%d", &s);
        num[i] = s;
        sum += s;
        while(s--) {
            int x; scanf("%d", &x);
            V[i].push_back(x);
        }
    }

    min_cnt = sum / n;
    int need = sum % n;

    for(int i = 1; i <= n && need; i++) {
        if(num[i] >= min_cnt + 1) {
            gg[i] = true;
            need--;
        }
    }

    for(int i = 1; i <= n; i++) {
        if(num[i] > min_cnt) {
            tar[i] = gg[i] ? min_cnt + 1 : min_cnt;
            if(num[i] > tar[i]) {
                for(auto &t : V[i]) {
                    P[t].push_back(i);
                }
            }
        }
        else if(num[i] < min_cnt || need && num[i] == min_cnt) {
            if(need) tar[i] = min_cnt + 1, need--;
            else tar[i] = min_cnt;
            for(auto &t : V[i]) {
                T[t].push_back(i);
            }
            S.insert(i);
        }
    }

    for(int i = 1; i <= m; i++) {
        for(auto &id : T[i]) {
            vis[id] = i;
        }
        int pt = 0;
        while(pt < P[i].size() && ban[P[i][pt]]) pt++;
        vector<int> del;
        for(auto &id : S) {
            if(pt >= P[i].size()) break;
            if(vis[id] == i) continue;
            ans.push_back(mk(mk(P[i][pt], id), i));
            num[P[i][pt]]--;
            if(num[P[i][pt]] == tar[P[i][pt]]) {
                ban[P[i][pt]] = true;
            }
            num[id]++;
            if(num[id] == tar[id]) {
                del.push_back(id);
            }
            pt++;
            while(pt < P[i].size() && ban[P[i][pt]]) pt++;
        }
        for(auto &id : del) S.erase(id);
    }

    printf("%d\n", (int)ans.size());
    for(auto &t : ans) {
        printf("%d %d %d\n", t.fi.fi, t.fi.se, t.se);
    }
    return 0;
}

/*
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