Codeforces Gym101234G Dreamoon and NightMarket(优先队列,子集和第k大)
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题意:
求子集和第k大,n,k<=1e6
思路:
优先队列经典题目,注意优先队列是默认按从大到小排的
代码:
#include<iostream> #include<cstdio> #include<algorithm> #include<cmath> #include<cstring> #include<string> #include<stack> #include<queue> #include<deque> #include<set> #include<vector> #include<map> #define fst first #define sc second #define pb push_back #define mem(a,b) memset(a,b,sizeof(a)) #define lson l,mid,root<<1 #define rson mid+1,r,root<<1|1 #define lc root<<1 #define rc root<<1|1 #define lowbit(x) ((x)&(-x)) using namespace std; typedef double db; typedef long double ldb; typedef long long ll; typedef unsigned long long ull; typedef pair<int,int> PI; typedef pair<ll,ll> PLL; const db eps = 1e-6; const int mod = 1e9+7; const int maxn = 4e5+100; const int maxm = 4e5+100; const int inf = 0x3f3f3f3f; const db pi = acos(-1.0); int n, k; ll a[maxn]; priority_queue<pair<ll, int> ,vector<pair<ll,int>>, greater<pair<ll,int>> >q; //priority_queue<pair<ll,int>, vector<pair<ll,int> >, greater<pair<ll,int> > >q; int main(){ scanf("%d %d", &n, &k); for(int i = 1; i <= n; i++){ scanf("%lld", &a[i]); } sort(a+1,a+1+n); q.push({a[1],1}); int cnt = 0; while(cnt < k){ auto tmp = q.top(); q.pop(); ll ans = tmp.fst; int id = tmp.sc; if(id < n){ q.push({ans+a[id+1],id+1}); q.push({ans-a[id]+a[id+1], id+1}); } cnt++; if(cnt == k){ printf("%lld ", ans); break; } } return 0; }
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