Submission #765253

#	Time	Username	Problem	Language	Result	Execution time	Memory
765253		oyber	Joker (BOI20_joker)	C++14	0 / 100	58 ms	3644 KiB

Joker

#include <cstdio>
#include <vector>
#include <algorithm>
#include <functional>
using namespace std;

vector<int> u;
vector<int> s;
vector<int> p;

int find(int n) {
    if (u[n] == n) return n;
    return find(u[n]);
}

int parity(int n) {
    if (u[n] == n) return 0;
    return parity(u[n])^p[n];
}

void unite(int a, int b) {
    int ap = find(a);
    int bp = find(b);
    if (s[bp] > s[ap]) {
        swap(a, b);
        swap(ap, bp);
    }
    u[bp] = ap;
    s[ap] += s[bp];
    if (parity(a) == parity(b)) {
        p[bp] = 1;
    }
}

int main() {
    int n, m, qn;
    scanf("%d %d %d", &n, &m, &qn);

    u.resize(n);
    s.resize(n, 1);
    p.resize(n);

    for (int i = 0; i < n; i++) {
        u[i] = i;
    }

    vector<pair<int, int>> e(m);
    for (int i = 0; i < m; i++) {
        int a, b; 
        scanf("%d %d", &a, &b);
        a--;b--;
        e[i] = make_pair(a, b);
        //printf("%d %d %d\n", a, b, i);
    }

    int cycle = -1;
    for (int j = m-1; j >= 0; j--) {
        int a = e[j].first;
        int b = e[j].second;
        //printf("%d: (%d %d) (%d %d) (%d %d)\n", j, a, b, find(a), find(b), parity(a), parity(b));
        if (find(a) == find(b)) {
            if (parity(a) == parity(b)) {
                cycle = j;
                break;
            }
        } else {
            unite(a, b);
        }
    }
    //printf("%d\n", cycle);
    for (int i = 0; i < qn; i++) {
        int l, r;
        scanf("%d %d", &l, &r);
        l--;r--;

        if (r <= cycle) {
            printf("YES\n");
        } else {
            printf("NO\n");
        }
    }
}

Compilation message (stderr)

Joker.cpp: In function 'int main()':
Joker.cpp:37:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   37 |     scanf("%d %d %d", &n, &m, &qn);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Joker.cpp:50:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 |         scanf("%d %d", &a, &b);
      |         ~~~~~^~~~~~~~~~~~~~~~~
Joker.cpp:73:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   73 |         scanf("%d %d", &l, &r);
      |         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 6
• Subtask 2: 0 / 8
• Subtask 3: 0 / 25
• Subtask 4: 0 / 10
• Subtask 5: 0 / 22
• Subtask 6: 0 / 29