Submission #59291

#	Time	Username	Problem	Language	Result	Execution time	Memory
59291		gabrielsimoes	Duathlon (APIO18_duathlon)	C++17	23 / 100	178 ms	22996 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
const int MAXN = 1e5+10;
const int MAXM = 2e5+10;

int n, m;
vector<int> g[MAXN];
ll sub[MAXN];
bool ok[MAXN];

void dfs0(int cur, int pre) {
    if (ok[cur]) return;
    ok[cur] = 1;
    sub[cur] = 1;
    for (int nx : g[cur]) {
        if (nx != pre) {
            dfs0(nx, cur);
            sub[cur] += sub[nx];
        }
    }
}

ll ans = 0;
void dfs1(int cur, int pre, ll sum = 0) {
    if (ok[cur]) return;
    ok[cur] = 1;
    ans += 2 * sum * (sub[cur]-1);

    // printf("dfs1 %d %lld %lld: ans %lld\n", cur, sum, sub[cur], ans);

    for (int nx : g[cur]) {
        if (nx != pre) {
            ans += (sub[cur]-1-sub[nx]) * sub[nx];
            dfs1(nx, cur, sum + sub[cur] - sub[nx]);
            // printf("dfs1 %d: ans %lld\n", cur, ans);
        }
    }
}

int main() {
    scanf("%d%d", &n, &m);

    for (int i = 0,a,b; i < m; i++) {
        scanf("%d%d", &a, &b);
        g[a].push_back(b);
        g[b].push_back(a);
    }

    for (int i = 0; i < n; i++) dfs0(i, i);
    memset(ok, 0, sizeof(ok));
    for (int i = 0; i < n; i++) dfs1(i, i);

    printf("%lld\n", ans);
}

Compilation message (stderr)

count_triplets.cpp: In function 'int main()':
count_triplets.cpp:43:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d", &n, &m);
     ~~~~~^~~~~~~~~~~~~~~~
count_triplets.cpp:46:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d", &a, &b);
         ~~~~~^~~~~~~~~~~~~~~~

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