Submission #217952

#	Time	Username	Problem	Language	Result	Execution time	Memory
217952		perveevm	Duathlon (APIO18_duathlon)	C++14	10 / 100	1096 ms	29432 KiB

count_triplets

// #pragma comment(linker, "/stack:200000000")
// #pragma GCC optimize("Ofast,no-stack-protector")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
// #pragma GCC optimize("unroll-loops")

#include <bits/stdc++.h>

#ifdef PERVEEVM_LOCAL
    #define debug(x) std::cerr << (#x) << ":\t" << (x) << std::endl
#else
    #define debug(x) 238;
#endif

#define fastIO std::ios_base::sync_with_stdio(false); std::cin.tie(0); std::cout.tie(0)
#define NAME "File"

using ll = long long;
using ld = long double;

#ifdef PERVEEVM_LOCAL
    std::mt19937 rnd(238);
#else
    std::mt19937 rnd(std::chrono::high_resolution_clock::now().time_since_epoch().count());
#endif

const double PI = atan2(0.0, -1.0);
const int INF = 0x3f3f3f3f;
const ll LINF = (ll)2e18;
const int N = 200100;
const int LG = 18;

std::vector<int> g[N];
bool used[N];
int cmpId[N];
int sz = 0, curCmp = 0, timer = 0;
int dp[LG][N];
int tin[N], tout[N];
int h[N];

void dfs(int v, int p, int d) {
    used[v] = true;
    ++sz;
    cmpId[v] = curCmp;
    tin[v] = timer++;
    h[v] = d;

    dp[0][v] = p;

    for (auto to : g[v]) {
        if (!used[to]) {
            dfs(to, v, d + 1);
        }
    }

    tout[v] = timer++;
}

void precalcLCA() {
    for (int i = 1; i < LG; ++i) {
        for (int j = 0; j < N; ++j) {
            dp[i][j] = dp[i - 1][dp[i - 1][j]];
        }
    }
}

bool isParent(int a, int b) {
    return tin[a] <= tin[b] && tout[a] >= tout[b];
}

int lca(int a, int b) {
    if (isParent(a, b)) {
        return a;
    }
    if (isParent(b, a)) {
        return b;
    }

    for (int i = LG - 1; i >= 0; --i) {
        int pa = dp[i][a];

        if (!isParent(pa, b)) {
            a = pa;
        }
    }

    return dp[0][a];
}

int dist(int a, int b) {
    return h[a] + h[b] - 2 * h[lca(a, b)];
}

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

    for (int i = 0; i < m; ++i) {
        int from, to;
        scanf("%d%d", &from, &to);

        g[from - 1].push_back(to - 1);
        g[to - 1].push_back(from - 1);
    }

    for (int i = 0; i < n; ++i) {
        if (!used[i]) {
            dfs(i, i, 0);
            ++curCmp;
        }
    }

    precalcLCA();

    ll ans = 0;
    for (int from = 0; from < n; ++from) {
        for (int to = 0; to < n; ++to) {
            if (from == to || cmpId[from] != cmpId[to]) {
                continue;
            }

            ans += dist(from, to) - 1;
        }
    }

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

int main(void) {
    // freopen(NAME".in", "r", stdin);
    // freopen(NAME".out", "w", stdout);

    auto start = std::chrono::high_resolution_clock::now();
    run();
    auto end = std::chrono::high_resolution_clock::now();

    #ifdef PERVEEVM_LOCAL
        std::cerr << "Execution time: "
                  << std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count()
                  << " ms" << std::endl;
    #endif

    return 0;
}

Compilation message (stderr)

count_triplets.cpp: In function 'int main()':
count_triplets.cpp:132:10: warning: variable 'start' set but not used [-Wunused-but-set-variable]
     auto start = std::chrono::high_resolution_clock::now();
          ^~~~~
count_triplets.cpp:134:10: warning: variable 'end' set but not used [-Wunused-but-set-variable]
     auto end = std::chrono::high_resolution_clock::now();
          ^~~
count_triplets.cpp: In function 'void run()':
count_triplets.cpp:95:10: 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:99:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d", &from, &to);
         ~~~~~^~~~~~~~~~~~~~~~~~~~

• 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