Submission #59316

#	Time	Username	Problem	Language	Result	Execution time	Memory
59316		gabrielsimoes	Duathlon (APIO18_duathlon)	C++17	38 / 100	1096 ms	27344 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];

bool ok[MAXN];
int pre[MAXN];
int link[MAXN];
int t = 0;

int rep[MAXN];
void dfs0(int cur, int prev) {
    if (ok[cur]) return;
    ok[cur] = 1;
    link[cur] = pre[cur] = t++;
    rep[cur] = cur;

    for (int nx : g[cur]) {
        if (nx != prev) {
            if (ok[nx]) {
                link[cur] = min(link[cur], pre[nx]);
            } else {
                dfs0(nx, cur);
                link[cur] = min(link[cur], link[nx]);

                if (link[nx] <= pre[cur]) { // same component (not a bridge)
                    rep[nx] = rep[cur];
                }
            }
        }
    }
}

void normalize(int cur) {
    if (rep[cur] != cur) {
        normalize(rep[cur]);
        rep[cur] = rep[rep[cur]];
    }
}

vector<int> comp[MAXN];
ll sz[MAXN], sub[MAXN], subComp[MAXN];
void dfs1(int cur, int prev) {
    if (ok[cur]) return;
    ok[cur] = 1;

    sz[rep[cur]]++;
    comp[rep[cur]].push_back(cur);

    for (int nx : g[cur]) {
        if (nx != prev) {
            dfs1(nx, cur);
            if (rep[nx] != rep[cur]) {
                sub[cur] += subComp[rep[nx]] + sz[rep[nx]];
            }
        }
    }

    subComp[rep[cur]] += sub[cur];
}

ll ans = 0;
void dfs2(int cur, int prev, ll sum = 0) {
    if (ok[cur]) return;
    ok[cur] = 1;

    sub[cur] += sum;
    subComp[cur] += sum;

    // printf("sz %lld: %lld\n", sz[cur], sz[cur] * (sz[cur] - 1) * (sz[cur] - 2));
    // ans += sz[cur] * (sz[cur] - 1) * (sz[cur] - 2);

    // printf("%d, %d ~ sum %lld ~ ans %ld\n", cur, prev, sum, ans);

    for (int v : comp[cur]) {
        ok[v] = true;
        for (int nx : g[v]) {
            if (nx != prev && rep[nx] != cur) {
                // printf("\t%d ~> %d %lld %lld %lld %lld\n", v, nx, subComp[cur], sz[cur], -subComp[nx], -sz[nx]);
                dfs2(nx, v, subComp[cur] + sz[cur] - subComp[nx] - sz[nx]);
                ans += (subComp[nx] + sz[nx]) * (sub[v] - subComp[nx] - sz[nx]);
                // printf("%d -> %d: %lld * %lld\n", v, nx, subComp[nx] + sz[nx], sub[v] - subComp[nx] - sz[nx]);
            } else if (nx == prev) {
                ans += sum * (sub[v] - sum);
                // printf("%d -> %d: %lld * %lld\n", v, nx, sum, sub[v] - sum);
            }
        }
    }

    for (int u : comp[cur]) {
        ans += 2LL * sub[u] * (sz[cur] - 1LL + subComp[cur] - sub[u]);

        for (int v : comp[cur]) {
            if (u != v) {
                ans += (sub[u] + 1LL) * (sub[v] + 1LL) * (sz[cur] - 2LL);
            }
        }
    }

    sub[cur] -= sum;
    subComp[cur] -= sum;
}

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 = 1; i <= n; i++) dfs0(i, i);
    for (int i = 1; i <= n; i++) normalize(i);
    memset(ok, 0, sizeof(ok));
    for (int i = 1; i <= n; i++) dfs1(i, i);
    memset(ok, 0, sizeof(ok));
    // for (int i = 1; i <= n; i++) printf("%d: rep %d sub %d\n", i, rep[i], sub[i]);
    // for (int i = 1; i <= n; i++) if(i == rep[i]) printf("comp %d: sz %d, subComp %d\n", i, sz[i], subComp[i]);
    for (int i = 1; i <= n; i++) dfs2(i, i);

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

Compilation message (stderr)

count_triplets.cpp: In function 'int main()':
count_triplets.cpp:110:10: 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:113:14: 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: 15 / 15
• Subtask 7: 0 / 20
• Subtask 8: 0 / 8
• Subtask 9: 0 / 10