HDU 6533 (贪心&递推)
显然是对边排序，从小到大选，把图画一下，对每层进行递推，维护前一个层的 s u m sum sum，每次 s u m × n sum\times n sum×n，然后再加上当前层的边权即可。
// Problem: B - Build Tree
// Contest: Virtual Judge - 2019CCPC湖南全国邀请赛（广东省赛、江苏省赛）重现赛 [Cloned]
// URL: https://vjudge.net/contest/457173#problem/B
// Memory Limit: 65 MB
// Time Limit: 1500 ms
// Date: 2021-09-08 16:31:43
// --------by Herio--------
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int N=2e5+5,M=2e4+5,inf=0x3f3f3f3f,mod=1e9+7;
#define mst(a,b) memset(a,b,sizeof a)
#define PII pair<int,int>
#define x first
#define y second
#define pb emplace_back
#define SZ(a) (int)a.size()
#define rep(i,a,b) for(int i=a;i<=b;++i)
#define per(i,a,b) for(int i=a;i>=b;--i)
#define IOS ios::sync_with_stdio(false),cin.tie(0)
void Print(int *a,int n){
for(int i=1;i<n;i++)
printf("%d ",a[i]);
printf("%d\n",a[n]);
}
ll k,m,n,p,sum,ans,id,now;
ll a[N];
int main(){
while(~scanf("%lld%lld%lld%lld",&k,&m,&n,&p)){
now=n,id=sum=ans=0;
rep(i,1,k) scanf("%lld",&a[i]);sort(a+1,a+k+1);
rep(i,2,m){
sum=sum*n%p;
rep(j,1,now) sum=(sum+a[++id])%p;
ans=(ans+sum)%p;
now*=n;
}printf("%lld\n",ans);
}
return 0;
}
