Submission #698664

#	Time	Username	Problem	Language	Result	Execution time	Memory
698664		vjudge1	Duathlon (APIO18_duathlon)	C++17	10 / 100	1088 ms	1048576 KiB

count_triplets

#include "bits/stdc++.h"
#define ll long long
using namespace std;
const ll mod = 1000000007;

vector<int> v[100001];
int anc[100001][20], d[100001];
int logg = 20;

void dfs(int x, int par) {
    for(int i : v[x]) {
        if(i != par) {
            anc[i][0] = x;
            d[i] = d[x] + 1;
            dfs(i, x);
        }
    }
}

int get_lca(int a, int b) {
    if(d[a] < d[b])
        swap(a, b);
    int dif = d[a] - d[b];
    for(int i = 0; i < logg; i++) {
        if(dif & (1 << i))
            a = anc[a][i];
    }
    if(a == b)
        return a;
    for(int i = logg - 1; i >= 0; i--) {
        if(anc[a][i] != anc[b][i]) {
            a = anc[a][i];
            b = anc[b][i];
        }
    }
    if(anc[a][0] == anc[b][0])
        return anc[a][0];
    return -1;
}

signed main () {
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    // freopen("cowland.in","r",stdin);
    // freopen("cowland.out","w",stdout);

    int n, m;
    cin >> n >> m;
    for(int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        v[a].push_back(b);
        v[b].push_back(a);
    }
    for(int i = 1; i <= n; i++) {
        if(!anc[i][0]) {
            anc[i][0] = i;
            dfs(i, 0);
        }
    }
    for(int j = 1; j < logg; j++) {
        for(int i = 1; i <= n; i++)
            anc[i][j] = anc[anc[i][j - 1]][j - 1];
    }
    ll ans = 0;
    for(int i = 1; i <= n; i++) {
        for(int j = i + 1; j <= n; j++) {
            int lca = get_lca(i, j);
            if(lca == -1)
                continue;
            ll dis = (d[i] + d[j]) - (d[lca] * 2);
            ans += ((dis - 1) * 2LL);
        }
    }
    cout << ans;

    return 0;
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 8
• Subtask 4: 10 / 10
• Subtask 5: 0 / 13
• Subtask 6: 0 / 15
• Subtask 7: 0 / 20
• Subtask 8: 0 / 8
• Subtask 9: 0 / 10