扩展域写法

#include <cstring>
#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;

const int N = 40010, Base = N / 2;

int n, m;
int p[N];
unordered_map<int, int> S;

int get(int x)
{
    if (S.count(x) == 0) S[x] = ++ n;
    return S[x];
}

int find(int x)
{
    if (p[x] != x) p[x] = find(p[x]);
    return p[x];
}

int main()
{
    cin >> n >> m;
    n = 0;

    for (int i = 0; i < N; i ++ ) p[i] = i;

    int res = m;
    for (int i = 1; i <= m; i ++ )
    {
        int a, b;
        string type;
        cin >> a >> b >> type;
        a = get(a - 1), b = get(b);

        if (type == "even")
        {
            if (find(a + Base) == find(b))
            {
                res = i - 1;
                break;
            }
            p[find(a)] = find(b);
            p[find(a + Base)] = find(b + Base);
        }
        else
        {
            if (find(a) == find(b))
            {
                res = i - 1;
                break;
            }

            p[find(a + Base)] = find(b);
            p[find(a)] = find(b + Base);
        }
    }

    cout << res << endl;

    return 0;
}