Submission #1213698

#	Time	Username	Problem	Language	Result	Execution time	Memory
1213698		wcarrotw	Race (IOI11_race)	C++17	100 / 100	892 ms	41224 KiB

race

#include<bits/stdc++.h>
#define fi first
#define se second
#define ll long long
#define bit(mask, i) ((mask >> i) & 1)
#define pb push_back

using namespace std;

void minn(int &x, int y) {x < y ? x : (x = y);}

const int maxN = 200005;
int n, res; ll k; bool check[maxN]; vector<pair<int, ll>> a[maxN]; int sz[maxN];
map<ll, int> mp;

int get_sz(int u, int p) {
    sz[u] = 1;
    for(auto it : a[u]) {
        if(!check[it.fi] && it.fi != p) {
            sz[u] += get_sz(it.fi, u);
        }
    }
    return sz[u];
}

int findCentroid(int u, int p, int sized) {
    for(auto it : a[u]) {
        if(!check[it.fi] && it.fi != p && sz[it.fi] > sized) return findCentroid(it.fi, u, sized);
    }
    return u;
}

void update(int u, int par, bool upd, ll dist, int depth = 1) {
    if(dist > k) return;
    if(upd) {
        if(mp.find(dist) != mp.end()) {
            minn(mp[dist], depth);
        } else {
            mp[dist] = depth;
        }
    } else {
        if(mp.find(k - dist) != mp.end()) {
            minn(res, depth + mp[k - dist]);
        }
    }
    for(auto it : a[u]) {
        if(!check[it.fi] && it.fi != par) {
            update(it.fi, u, upd, dist + it.se, depth + 1);
        }
    }
}

void decomposition(int node) {
    int root = findCentroid(node, 0, get_sz(node, 0) >> 1);
    check[root] = 1;
    for(auto it : a[root]) {
        if(!check[it.fi]) {
            update(it.fi, root, 0, it.se);
            update(it.fi, root, 1, it.se);
        }
    }
    mp.clear();
    mp[0] = 0;
    for(auto it : a[root]) {
        if(!check[it.fi]) {
            decomposition(it.fi);
        }
    }
}

int best_path(int N, int K, int H[][2], int L[]) {
    n = N, k = K;
    for(int i = 1; i < n; ++i) {
        int u = H[i - 1][0], v = H[i - 1][1]; ll w = L[i - 1];
        ++u, ++v;
        a[u].pb({v, w}); a[v].pb({u, w});
    }
    res = INT_MAX;
    mp[0] = 0;
    decomposition(1);
    return (res == INT_MAX ? -1 : res);
}

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 22 / 22
• Subtask 4: 57 / 57