CF1270E Divide Points 题解

#pragma GCC optimize(3, "Ofast", "inline")
#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 500010;
int x[N], y[N];
signed main() {
    cout << fixed << setprecision(15);
    cin.tie(0)->sync_with_stdio(false);
    int n;
    cin >> n;
    for (int i = 1; i <= n; ++i) {
        cin >> x[i] >> y[i];
    }
    while (1) {
        int c1 = 0, c2 = 0;
        for (int i = 1; i <= n; ++i)
            if ((x[i] + y[i]) & 1) ++c1;
            else ++c2;
        if (c1 && c2) {
            vector<int> v;
            for (int i = 1; i <= n; ++i)
                if ((x[i] + y[i]) & 1) v.emplace_back(i);
            cout << v.size() << '\n';
            for (int &i : v) cout << i << ' ';
            cout << '\n';
            return 0;
        } else {
            for (int i = 1; i <= n; ++i) {
                if (c1) ++x[i];
            }
            for (int i = 1; i <= n; ++i) {
                int _x = x[i], _y = y[i];
                x[i] = (_x+_y) / 2, y[i] = (_x-_y) / 2;
            }
        }
    }
    return 0;
}