Connected Components? CodeForces - 920E (bfs)

大意:给定无向图, 求补图的连通块数

bfs模拟即可, 用了map存图, set维护未划分的点集, 复杂度$O(nlog^2n)$, 用链表的话可以$O(n)$

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <set>
#include <map>
#include <queue>
#define REP(i,a,n) for(int i=a;i<=n;++i)
#define pb push_back

using namespace std;

const int N = 4e5+, INF = 0x3f3f3f3f;
int n, m;
map<int,int> a[N];
set<int> s;
int sz[N];

int main() {
    scanf("%d%d", &n, &m);
    REP(i,,m) {
        int u, v;
        scanf("%d%d", &u, &v);
        a[u][v]=a[v][u]=;
    }
    REP(i,,n) s.insert(i);
    REP(i,,n) if (s.count(i)) {
        queue<int> q;
        q.push(i);
        int cnt = ;
        while (!q.empty()) {
            int i=q.front();q.pop();
            vector<int> tmp;
            for (int j:s) if (!a[i][j]) {
                ++cnt, q.push(j), tmp.pb(j);
            }
            for (int j:tmp) s.erase(j);
        }
        sz[++*sz] = cnt;
    }
    printf("%d\n", *sz);
    sort(sz+,sz++*sz);
    REP(i,,*sz) printf("%d ",sz[i]);
    puts("");
}