Submission #566312

#	Time	Username	Problem	Language	Result	Execution time	Memory
566312		hoanghq2004	Alternating Current (BOI18_alternating)	C++14	0 / 100	3116 ms	808736 KiB

alternating

#include <bits/stdc++.h>
#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;
using namespace std;

template <typename T>
using ordered_set = tree <T, null_type, less <T>, rb_tree_tag, tree_order_statistics_node_update>;

const int N = 1e5 + 10;

int n, m, k;
vector <int> s[N], g[N];
int color[N];

int dfs(int u, int c) {
    if (color[u] != -1) return (color[u] == c);
    color[u] = c;
    for (auto v: g[u]) {
        if (!dfs(v, c ^ 1)) return 0;
    }
    return 1;
}

int main() {
    ios :: sync_with_stdio(0); cin.tie(0);
    cin >> n >> m;
    for (int i = 1; i <= m; ++i) {
        int L, R;
        cin >> L >> R;
        if (L <= R) {
            for (int j = L; j <= R; ++j)
                s[j].push_back(i);
        } else {
            for (int j = L; j <= n; ++j)
                s[j].push_back(i);
            for (int j = 1; j <= R; ++j)
                s[j].push_back(i);
        }
    }
    for (int i = 1; i <= n; ++i) {
        if (s[i].size() < 2) {
            cout << "impossible\n";
            exit(0);
        }
        if (s[i].size() == 2) {
            g[s[i][0]].push_back(s[i][1]);
            g[s[i][1]].push_back(s[i][0]);
        }
    }
    memset(color, -1, sizeof(color));
    for (int i = 1; i <= n; ++i) {
        int ok0 = 0, ok1 = 0;
        for (auto j: s[i]) {
            if (color[j] == 0) ok0 = 1;
            if (color[j] == 1) ok1 = 1;
        }
        if (ok0 && ok1) continue;
        random_shuffle(s[i].begin(), s[i].end());
        if (!ok0) {
            for (auto j: s[i]) {
                if (color[j] == -1) {
                    if (!dfs(j, 0)) {
                        cout << "impossible\n";
                        exit(0);
                    }
                    ok0 = 1;
                }
            }
            if (!ok0) {
                cout << "impossible\n";
                exit(0);
            }
        }
        for (auto j: s[i])
            if (color[j] == 1) ok1 = 1;
        if (ok1) continue;
        random_shuffle(s[i].begin(), s[i].end());
        for (auto j: s[i]) {
            if (color[j] == -1) {
                if (!dfs(j, 1)) {
                    cout << "impossible\n";
                    exit(0);
                }
                ok1 = 1;
            }
        }
        if (!ok1) {
            cout << "impossible\n";
            exit(0);
        }
    }
    for (int i = 1; i <= m; ++i) cout << color[i];
}

• Subtask 1: 0 / 13
• Subtask 2: 0 / 20
• Subtask 3: 0 / 22
• Subtask 4: 0 / 19
• Subtask 5: 0 / 26