Submission #311581

#	Time	Username	Problem	Language	Result	Execution time	Memory
311581		Hehehe	Pipes (BOI13_pipes)	C++14	100 / 100	152 ms	85112 KiB

pipes

#include<bits/stdc++.h> //:3
using namespace std;
typedef long long ll;
#define all(a) (a).begin(), (a).end()
#define ff first
#define ss second
#define pb push_back
#define mp make_pair
#define pi pair<int, int>
#define sz(x) (int)((x).size())
//#define int long long


const int dx[] = {0, 1, 0, -1};
const int dy[] = {1, 0, -1, 0};

const ll inf = 2e6;
const ll mod = 1e9 + 7;
const int N = 3e6 + 11;
const ll INF64 = 3e18 + 1;
const double eps = 1e-14;
const double PI = acos(-1);

//ifstream in(".in");
//ofstream out(".out");

int n, m;
vector<pi> v[N];
ll val[N], vis[N], C[N], d[N], L = -1, R, ID = -1, bb, s;

void dfs(int nod, int p) {

    	ll cur = C[nod];
    	vis[nod] = 1;

    	if(d[nod] & 1) s -= C[nod];else s += C[nod];

    	for(auto i : v[nod]){
            int it = i.ff, id = i.ss;
            if(it == p)continue;
    		if(!vis[it]) {
    			d[it] = d[nod] + 1;
    			dfs(it, nod);
    		}else
    		if(d[it] < d[nod]) {
    			if(d[it] % 2 != d[nod] % 2){
                    cout << "0\n";
                    exit(0);
                }
    			L = it, R = nod, ID = id, bb = d[nod] & 1;
    		}
    	}
}

ll recover(int nod, int p) {
    ll cur = C[nod];
    for(auto i : v[nod]){
        int it = i.ff, id = i.ss;
        if(it == p || id == ID)continue;
        ll t = recover(it, nod);
        val[id] = t;
        cur += t;
    }
    return -cur;
}



void solve(){

    cin >> n >> m;

    if(m > n){
        cout << "0" << '\n';
        return;
    }

    for(int i = 1; i <= n; i++) cin >> C[i];

    for(int i = 0, x, y; i < m; i++) {
        cin >> x >> y;
        v[x].push_back({y, i});
        v[y].push_back({x, i});
    }

    dfs(1, 1);

    if(L != -1) {

        if(bb) s *= -1;
        C[L] -= s/2;
        C[R] -= s/2;
        val[ID] = (-s)/2;
    }

    recover(1, 1);

    for(int i = 0; i < m; i++) cout << -2ll*val[i] << '\n';
}

int32_t main(){
ios_base :: sync_with_stdio(0); cin.tie(0); cout.tie(0);

    //cout << setprecision(6) << fixed;

    int T = 1;
    //cin >> T;
    while(T--){
        solve();
    }
}

Compilation message (stderr)

pipes.cpp: In function 'void dfs(int, int)':
pipes.cpp:33:9: warning: unused variable 'cur' [-Wunused-variable]
   33 |      ll cur = C[nod];
      |         ^~~

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