Submission #48294

#	Time	Username	Problem	Language	Result	Execution time	Memory
48294		choikiwon	전압 (JOI14_voltage)	C++17	100 / 100	283 ms	55644 KiB

voltage

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

typedef pair<int, int> pii;

const int MN = 100010;

int N, M;
vector<int> adj[MN], U, V;
int tin[MN], tout[MN], col[MN], timer, cnt;

struct Fenwick {
    vector<int> tree;
    void init() {
        tree = vector<int>(N + 1, 0);
    }
    void upd(int idx, int val) {
        for(int i = idx + 1; i <= N; i += (i & -i)) tree[i] += val;
    }
    int quer(int a) {
        int ret = 0;
        for(int i = a + 1; i >= 1; i -= (i & -i)) ret += tree[i];
        return ret;
    }
    int quer(int a, int b) {
        return quer(b) - quer(a - 1);
    }
} bit1, bit2;
priority_queue<pii> pq1, pq2;
int ans;

void dfs0(int u, int fe) {
    tin[u] = timer++;
    for(int i = 0; i < adj[u].size(); i++) {
        int e = adj[u][i];
        int v = U[e] + V[e] - u;
        if(e == fe) continue;
        if(tin[v] == -1) {
            col[v] = col[u] ^ 1;
            dfs0(v, e);
        }
        else if(tin[v] < tin[u]) {
            if(col[v] == col[u]) cnt++;
        }
    }
}

void dfs1(int u, int fe) {
    tin[u] = timer++;
    for(int i = 0; i < adj[u].size(); i++) {
        int e = adj[u][i];
        int v = U[e] + V[e] - u;
        if(e == fe) continue;
        if(tin[v] == -1) {
            dfs1(v, e);
        }
        else if(tin[v] < tin[u]) {
            if(col[v] == col[u]) pq1.push({ tin[v], tin[u] }), bit1.upd(tin[u], 1);
            else pq2.push({ tin[v], tin[u] }), bit2.upd(tin[u], 1);
        }
    }
    tout[u] = timer;

    while(!pq1.empty() && pq1.top().first >= tin[u]) bit1.upd(pq1.top().second, -1), pq1.pop();
    while(!pq2.empty() && pq2.top().first >= tin[u]) bit2.upd(pq2.top().second, -1), pq2.pop();
    if(fe != -1 && bit1.quer(tin[u], tout[u] - 1) == cnt && !bit2.quer(tin[u], tout[u] - 1)) ans++;
}

int main() {
    scanf("%d %d", &N, &M);

    int loop = 0;
    for(int i = 0; i < M; i++) {
        int u, v; scanf("%d %d", &u, &v);
        u--; v--;

        if(u == v) {
            loop++;
            continue;
        }

        adj[u].push_back(U.size());
        adj[v].push_back(U.size());
        U.push_back(u);
        V.push_back(v);
    }

    if(loop >= 2) {
        printf("0");
        return 0;
    }

    memset(tin, -1, sizeof(tin));
    for(int i = 0; i < N; i++) if(tin[i] == -1) {
        dfs0(i, -1);
    }

    if(loop) {
        if(!cnt) printf("1");
        else printf("0");
        return 0;
    }

    memset(tin, -1, sizeof(tin));
    timer = 0;
    bit1.init();
    bit2.init();
    for(int i = 0; i < N; i++) if(tin[i] == -1) {
        dfs1(i, -1);
    }

    if(cnt == 1) ans++;
    printf("%d", ans);
}

Compilation message (stderr)

voltage.cpp: In function 'void dfs0(int, int)':
voltage.cpp:34:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0; i < adj[u].size(); i++) {
                    ~~^~~~~~~~~~~~~~~
voltage.cpp: In function 'void dfs1(int, int)':
voltage.cpp:50:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0; i < adj[u].size(); i++) {
                    ~~^~~~~~~~~~~~~~~
voltage.cpp: In function 'int main()':
voltage.cpp:70:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d", &N, &M);
     ~~~~~^~~~~~~~~~~~~~~~~
voltage.cpp:74:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         int u, v; scanf("%d %d", &u, &v);
                   ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 35 / 35
• Subtask 4: 45 / 45