Kth Minimum Clique(2019年牛客多校第二场D题+k小团+bitset)

目录
  • 题目链接
  • 题意
  • 思路
  • 代码

题目链接

传送门

题意

找第\(k\)小团。

思路

用\(bitset\)来标记每个结点与哪些结点直接有边，然后进行\(bfs\)，在判断新加入的点与现在有的点是否都有边则直接用\(bitset\)与一下即可，记得去重。

代码

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;

typedef long long LL;
typedef pair pLL;
typedef pair pLi;
typedef pair pil;;
typedef pair pii;
typedef unsigned long long uLL;

#define lson (rt<<1),L,mid
#define rson (rt<<1|1),mid + 1,R
#define lowbit(x) x&(-x)
#define name2str(name) (#name)
#define bug printf("*********\n")
#define debug(x) cout<<#x"=["< vis[105];
int w[maxn], mp[maxn][maxn];
struct node {
    LL val;
    bitset<101> has;
    bool operator < (const node& x) const {
        return val > x.val;
    }
}nw;

priority_queue q;

int main() {
#ifndef ONLINE_JUDGE
    FIN;
#endif
    scanf("%d%d", &n, &k);
    for(int i = 1; i <= n; ++i) {
        scanf("%d", &w[i]);
        nw.has.set(i), nw.val = w[i];
        q.push(nw);
        nw.has.reset(i);
    }
    for(int i = 1; i <= n; ++i) {
        for(int j = 1; j <= n; ++j) {
            scanf("%1d", &mp[i][j]);
            if(mp[i][j]) vis[i].set(j);
        }
    }
    LL ans = -1;
    if(k == 1) {
        printf("0\n");
        return 0;
    }
    --k;
    while(!q.empty()) {
        nw = q.top(), q.pop();
        if(--k == 0) {
            ans = nw.val;
            break;
        }
        int idx = 1;
        for(int i = 1; i <= n; ++i) if(nw.has.test(i)) idx = i + 1;
        for(int i = idx; i <= n; ++i) {
            if(nw.has.test(i)) continue;
            if((vis[i] & nw.has) != nw.has) continue;
            nw.val += w[i];
            nw.has.set(i);
            q.push(nw);
            nw.val -= w[i];
            nw.has.reset(i);
        }
    }
    printf("%lld\n", ans);
    return 0;
}
比赛题解感想ACM小技巧

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