제출 #253849

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
253849		aZvezda	Pipes (BOI13_pipes)	C++14	74.07 / 100	252 ms	31096 KiB

pipes

#include <bits/stdc++.h>
using namespace std;
//#pragma GCC optimize ("O3")
//#pragma GCC target ("sse4")
#define endl "\n"
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
template<class T, class T2> inline bool chkmax(T &x, const T2 &y) { return x < y ? x = y, 1 : 0; }
template<class T, class T2> inline bool chkmin(T &x, const T2 &y) { return x > y ? x = y, 1 : 0; }
const ll mod = 1e9 + 7;
template<class T> inline void fix(T &x) {if(x >= mod | x <= -mod) {x %= mod;} if(x < 0) {x += mod;}}
#define out(x) cout << __LINE__ << ": " << (#x) << " = " << (x) << endl


//If we have an even cycle then we can add 1 on odd edges and -1 on even edges so the solutions stay the same. We can remove leaves one by one

const ll MAX_N = 1e5 + 10;
set<pair<ll, ll> > g[MAX_N];
ll ans[MAX_N], arr[MAX_N];

struct cmp {
    bool operator ()(const ll &a, const ll &b) const {
        if(g[a].size() == g[b].size()) {
            return a < b;
        }
        return g[a].size() < g[b].size();
    }
};

multiset<ll, cmp> pq;

void removeBranches() {
    while(!pq.empty() && g[*(pq.begin())].size() == 1) {
        ll curr = *(pq.begin()); pq.erase(pq.begin());
        auto other = *(g[curr].begin());
        pq.erase(other.first);
        ans[other.second] = 2 * arr[curr];
        arr[other.first] -= arr[curr];
        g[other.first].erase({curr, other.second});
        pq.insert(other.first);
    }
}

int rret = 0;

void dfs(int x, int p, int start, int flag) {
    rret += arr[x] * flag;
    //cout << x << " " << p << " " << ans[x] << " " << rret << endl;
    for(auto it : g[x]) {
        if(it.first == p || it.first == start) {continue;}
        dfs(it.first, x, start, -flag);
    }
}

void removeCycle() {
    if(pq.size() < 2) {return;}
    auto now = pq.begin();
    if(g[*now].size() > 2) {
        cout << 0 << endl;
        exit(0);
    }
    now = pq.end(); now --;
    if(g[*now].size() > 2) {
        cout << 0 << endl;
        exit(0);
    }
    if(pq.size() % 2 == 0) {
        cout << 0 << endl;
        exit(0);
    }
    int curr = *(pq.begin());
    dfs(curr, (*(g[curr].begin())).first, curr, 1);
    rret /= 2;
    auto sec = (g[curr].begin());
    arr[curr] -= rret;
    arr[(*sec).first] -= rret;
    ans[(*sec).second] = rret;
    pq.erase(curr);
    pq.erase((*sec).first);
    g[curr].erase(sec);
    g[(*sec).first].erase({curr, (*sec).second});
    pq.insert(curr);
    pq.insert((*sec).first);
    //cout << curr << " " << (*sec).first << " " << rret << endl;
}

signed main() {
    ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
    ll n, m;
    cin >> n >> m;
    if(m > n) {cout << 0 << endl; return 0;}
    for(ll i = 1; i <= n; i ++) {
        cin >> arr[i];
    }
    for(ll i = 0; i < m; i ++) {
        ll a, b;
        cin >> a >> b;
        g[a].insert({b, i});
        g[b].insert({a, i});
    }
    for(ll i = 1; i <= n; i ++) {
        pq.insert(i);
    }
    removeBranches();
    removeCycle();
    removeBranches();
    for(ll i = 0; i < m; i ++) {
        cout << ans[i] << endl;
    }
    return 0;
}

• Subtask 1: 30 / 30
• Subtask 2: 44.074074074074076 / 70