Submission #264811

#	Time	Username	Problem	Language	Result	Execution time	Memory
264811		shayan_p	Fireworks (APIO16_fireworks)	C++14	7 / 100	6 ms	7424 KiB

fireworks

// only miss the sun when it starts to snow
 
#include<bits/stdc++.h>
 
#define F first
#define S second
#define PB push_back
#define sz(s) int((s).size())
#define bit(n,k) (((n)>>(k))&1)
 
using namespace std;
 
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
 
const int maxn=3e5+10,mod=1e9+7;
const ll inf=1e18;
 
vector<pii> v[maxn];
vector<ll> vec;
pll s[maxn];
ll ans;

int n, m;
bool good[maxn];

void dfs(int u){
    good[u]|= u >= n;
    for(pii p:v[u]){
	dfs(p.F);
	if(good[p.F]){
	    good[u] = 1;
	    s[p.F].F+= p.S;
	    s[p.F].S+= p.S;
	}
    }
    if(good[u] == 0)
	return;    
    vec.clear();
    ll num=0;
    for(pii p:v[u]){
	if(good[p.F]){
	    num-= s[p.F].S - s[p.F].F;
	    vec.PB( s[p.F].F ), vec.PB( s[p.F].S );
	}
    }
    sort(vec.begin(), vec.end() );
    if(sz(vec)){
	int mid=sz(vec)/2;
	s[u]={ vec[mid-1], vec[mid] };
	for(ll x:vec)
	    num+= abs( s[u].F - x );
	assert(num % 2 == 0);
	ans+= num/2;
    }
}

int main(){
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie();
 
    cin>>n>>m;
 
    for(int i=1;i<n+m;i++){
	int x,y; cin>>x>>y;
	v[--x].PB({i,y});
    }
    dfs(0);
    return cout<< ans <<endl,0;
}
// Deathly mistakes:
//  * Read the problem carefully.
//  * Check maxn.
//  * Overflows.
 
 
// #pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

• Subtask 1: 7 / 7
• Subtask 2: 0 / 19
• Subtask 3: 0 / 29
• Subtask 4: 0 / 45