Submission #890899

#	Time	Username	Problem	Language	Result	Execution time	Memory
890899		nahco314	Tug of War (BOI15_tug)	C++14	23 / 100	60 ms	4436 KiB

tug

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

#pragma GCC target("avx2")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")

void ng() {
    cout << "NO" << endl;
    exit(0);
}

int remove(int v, vector<set<tuple<int, int, int>>>& g) {
    if (g[v].size() == 1) {
        tuple<int, int, int> elt = *g[v].begin();
        int l = v;
        int r = get<0>(elt);
        int s = get<1>(elt);
        int i = get<2>(elt);
        g[l].erase({r, s, i});
        g[r].erase({l, s, i});
        return s + -remove(r, g);
    }
    return 0;
}

int dfs(int v, int used_e, int sign, vector<set<tuple<int, int, int>>>& g, vector<int>& seen) {
    seen[v] = sign;
    int res = 0;
    sign *= -1;
    for (auto [nxt, s, e] : g[v]) {
        if (e == used_e) continue;
        if (seen[nxt]) {
            if (seen[nxt] == sign) {
                continue;
            } else {
                ng();
            }
        }
        res += sign * s;
        res += dfs(nxt, e, sign, g, seen);
    }
    // cerr << v << " " << used_e << " " << sign << " " << res << endl;
    return res;
}

int main() {
    int n, k;
    cin >> n >> k;
    vector<set<tuple<int, int, int>>> g(2 * n);
    for (int i = 0; i < 2 * n; i++) {
        int l, r, s;
        cin >> l >> r >> s;
        l--;
        r--;
        r += n;
        g[l].emplace(r, s, i);
        g[r].emplace(l, s, i);
    }

    int cur_sum = 0;
    for (int i = 0; i < 2 * n; i++) {
        int sign = i < n ? 1 : -1;
        cur_sum += remove(i, g) * sign;
    }

    vector<int> nums;
    vector<int> seen(2 * n, 0);
    for (int i = 0; i < 2 * n; i++) {
        if (seen[i]) continue;
        if (g[i].size() == 0) continue;
        int l = i;
        int r = get<0>(*g[i].begin());
        int s = get<1>(*g[i].begin());
        int used_e = get<2>(*g[i].begin());

        int num = s + dfs(l, used_e, 1, g, seen);
        nums.push_back(num);
    }

    for (auto a : nums) {
        // cerr << "" << a << endl;
    }

    int m = nums.size();
    int mid = n * 20 / 2;
    bitset<600001> cur(0);
    cur.set(cur_sum + mid);

    for (int i = 0; i < m; i++) {
        int num = abs(nums[i]);
        cur <<= num;
        cur |= cur >> (2 * num);

        /*
        cerr << i << endl;
        for (int i = 0; i < 600001; i++) {
            if (cur.test(i)) {
                cerr << i - mid << " ";
            }
        }
        cerr << endl;
        */
    }

    for (int i = -k; i <= k; i++) {
        int num = mid + i;
        if (cur.test(num)) {
            cout << "YES" << endl;
            exit(0);
        }
    }

    cout << "NO" << endl;
}

Compilation message (stderr)

tug.cpp: In function 'int dfs(int, int, int, std::vector<std::set<std::tuple<int, int, int> > >&, std::vector<int>&)':
tug.cpp:31:15: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   31 |     for (auto [nxt, s, e] : g[v]) {
      |               ^
tug.cpp: In function 'int main()':
tug.cpp:73:13: warning: unused variable 'r' [-Wunused-variable]
   73 |         int r = get<0>(*g[i].begin());
      |             ^
tug.cpp:81:15: warning: unused variable 'a' [-Wunused-variable]
   81 |     for (auto a : nums) {
      |               ^

• Subtask 1: 0 / 18
• Subtask 2: 0 / 30
• Subtask 3: 23 / 23
• Subtask 4: 0 / 29