Submission #4064765

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Source Code Expand

#include <algorithm>
#include <iostream>
#include <vector>
#include <math.h>
#include <set>
#include <map>
#include <string>
#include <stack>
#include <queue>
#include <iomanip>
#include <numeric>
#include <tuple>
#include <bitset>
#include <complex>
#include <unistd.h>
#include <cassert>
#include <cctype>
#include <random>
#include <time.h>
#define _USE_MATH_DEFINES
#define _GLIBCXX_DEBUG
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> plglg;
typedef pair<double, ll> pdlg;
typedef tuple<int, int, int> tiii;
typedef tuple<ll, ll, ll> tlglglg;
typedef tuple<double, double, double> tddd;
typedef complex<double> xy_t;
typedef vector<ll> vll;
typedef vector< vector<ll> > matrix;
#define REP(i, x, y) for(ll i = (ll)x; i < (ll)y; i++)
#define DREP(i, x, y, d) for(ll i = (ll)x; i < (ll)y; i += (ll)d)
#define PER(i, x, y) for(ll i = (ll)x; i > (ll)y; i--)
#define DPER(i, x, y, d) for(ll i = (ll)x; i > (ll)y; i -= (ll)d)
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
double pi = 3.141592653589793;
ll mod = 1000000007;
int intmax = 2147483647;
int intmin = -2147483648;
ll llmax = 9223372036854775807;
ll llmin = -9223372036854775807;
int iinf = intmax / 8;
ll inf = llmax / 8;
double eps = 1e-11;

struct edge {
    ll to, cost;
};

int V;
vector<edge> G[1000000];
ll d[1000000];

void addedge(int st, int ed, ll co) {
    edge e;
    e.to = ed;
    e.cost = co;
    G[st].push_back(e);
}

bool bipartite() {
    fill(d, d + V, -1);
    while (true) {
        int num = 0;
        for (int i = num; i < V; i++) {
            if (d[num] == -1) {
                break;
            }
            num++;
        }
        if (num == V) {
            return true;
        }
        d[num] = 0;
        queue<int> que;
        que.push(num);
        while (que.size() > 0) {
            int base = que.front();
            que.pop();
            int s = G[base].size();
            for (int i = 0; i < s; i++) {
                int to = G[base][i].to;
                if (d[to] == -1) {
                    if (d[base] == 0) {
                        d[to] = 1;
                    } else {
                        d[to] = 0;
                    }
                    que.push(to);
                } else {
                    if (d[to] == 1 && d[base] == 1) {
                        return false;
                    } else if (d[to] == 0 && d[base] == 0) {
                        return false;
                    }
                }
            }
        }
    }
}

int main() {
    ll N, M;
    cin >> N >> M;
    V = N;
    REP(i, 0, M) {
        ll a, b;
        cin >> a >> b;
        addedge(a - 1, b - 1, 1);
        addedge(b - 1, a - 1, 1);
    }
    bool ok = bipartite();
    if (ok) {
        ll zero = 0, one = 0;
        REP(i, 0, N) {
            if (d[i] == 0) {
                zero++;
            } else {
                one++;
            }
        }
        cout << zero * one - M << endl;
    } else {
        cout << N * (N - 1) / 2 - M << endl;
    }
}

Submission Info

Judge Result