結果

問題 No.1333 Squared Sum
ユーザー fastmath
提出日時 2021-01-08 22:18:52
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 314 ms / 2,000 ms
コード長 4,342 bytes
コンパイル時間 1,922 ms
コンパイル使用メモリ 197,692 KB
最終ジャッジ日時 2025-01-17 12:31:21
ジャッジサーバーID
（参考情報） 		judge1 / judge1
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ファイルパターン 結果
other AC * 44
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ソースコード

diff #
プレゼンテーションモードにする

#include<bits/stdc++.h>
using namespace std;
#define int long long
#define ii pair <int, int>
#define app push_back
#define all(a) a.begin(), a.end()
#define bp __builtin_popcountll
#define ll long long
#define mp make_pair
#define x first
#define y second
#define Time (double)clock()/CLOCKS_PER_SEC
#define debug(x) std::cout << #x << ": " << x << '\n';
#define FOR(i, n) for (int i = 0; i < n; ++i)
#define pb push_back
#define trav(a, x) for (auto& a : x)
using vi = vector<int>;
template <typename T>
std::ostream& operator <<(std::ostream& output, const pair <T, T> & data)
{
    output << "(" << data.x << "," << data.y << ")";
    return output;
}
template <typename T>
std::ostream& operator <<(std::ostream& output, const std::vector<T>& data)
{
    for (const T& x : data)
        output << x << " ";
    return output;
}
//ll div_up(ll a, ll b) { return a/b+((a^b)>0&&a%b); } // divide a by b rounded up
//ll div_down(ll a, ll b) { return a/b-((a^b)<0&&a%b); } // divide a by b rounded down 
#define tcT template<class T
#define tcTU tcT, class U
tcT> using V = vector<T>; 
tcT> void re(V<T>& x) { 
    trav(a, x)
        cin >> a;
}
tcT> bool ckmin(T& a, const T& b) {
    return b < a ? a = b, 1 : 0; 
} // set a = min(a,b)
tcT> bool ckmax(T& a, const T& b) {
    return a < b ? a = b, 1 : 0; 
}
//need define int long long
namespace Stuff {
const int MOD = 1e9+7;
int mod(int n) {
    n %= MOD;
    if (n < 0) return n + MOD;
    else return n;
}   
int fp(int a, int p) {
    int ans = 1, c = a;
    for (int i = 0; (1ll << i) <= p; ++i) {
        if ((p >> i) & 1) ans = mod(ans * c);
        c = mod(c * c);
    }   
    return ans;
}   
int dv(int a, int b) { return mod(a * fp(b, MOD - 2)); }
};
struct M {
ll x;
M (int x_) { x = Stuff::mod(x_); }   
M () { x = 0; }
M operator + (M y) {
    int ans = x + y.x;
    if (ans >= Stuff::MOD)
        ans -= Stuff::MOD;
    return M(ans);
}
M operator - (M y) {
    int ans = x - y.x;
    if (ans < 0)
        ans += Stuff::MOD;
    return M(ans);            
}   
M operator * (M y) { return M(x * y.x % Stuff::MOD); }   
M operator / (M y) { return M(x * Stuff::fp(y.x, Stuff::MOD - 2) % Stuff::MOD); }   
M operator + (int y) { return (*this) + M(y); }
M operator - (int y) { return (*this) - M(y); }   
M operator * (int y) { return (*this) * M(y); }   
M operator / (int y) { return (*this) / M(y); }   
M operator ^ (int p) { return M(Stuff::fp(x, p)); }   
void operator += (M y) { *this = *this + y; }   
void operator -= (M y) { *this = *this - y; }   
void operator *= (M y) { *this = *this * y; }
void operator /= (M y) { *this = *this / y; }   
void operator += (int y) { *this = *this + y; }   
void operator -= (int y) { *this = *this - y; }   
void operator *= (int y) { *this = *this * y; }
void operator /= (int y) { *this = *this / y; }   
void operator ^= (int p) { *this = *this ^ p; }
bool operator == (M y) { return x == y.x; }
};  
std::ostream& operator << (std::ostream& o, const M& a)
{
    cout << a.x;
    return o;
}
const int N = 2e5+7;
int n;
V <ii> g[N];
M sub[N], sum[N], cnt[N];
void dfs1(int u, int p) {
    cnt[u] = 1;
    trav (e, g[u]) {
        int v = e.x, c = e.y;
        M w = c;
        if (v != p) {
            dfs1(v, u);
            cnt[u] += cnt[v];
            sum[u] += sum[v];
            sum[u] += w * cnt[v];
            sub[u] += sub[v];
            sub[u] += w * 2 * sum[v]; 
            sub[u] += w * w * cnt[v];
        }   
    }   
}   
M ans = 0;
M dist[N];
M res[N];
void dfs2(int u, int p) {
    //debug(u);
    //debug(res[u]);
    ans += res[u];
    trav (e, g[u]) {
        int v = e.x, c = e.y;
        M w = c;
        if (v != p) {
            M down = sum[v] + w * cnt[v];
            M up = dist[u] - down;
            res[v] = res[u] + (w^2) * n + (w * 2) * (up - down);
            dist[v] = dist[u] - cnt[v] * w + (M(n) - cnt[v]) * w;
            dfs2(v, u);
        }   
    }   
}   
signed main() {
    #ifdef HOME
    freopen("input.txt", "r", stdin);
    #else
    #define endl '\n'
    ios_base::sync_with_stdio(0); cin.tie(0);
    #endif
    cin >> n;
    FOR (i, n - 1) {
        int u,v,w;
        cin >> u >> v >> w;
        g[u].app(mp(v, w));
        g[v].app(mp(u, w));
    }   
    dfs1(1, 1);
    res[1] = sub[1];
    dist[1] = sum[1];
    dfs2(1, 1);
    cout << ans/2 << endl;
}
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