贪心模拟，边权越小越靠近根节点。
#include<bits/stdc++.h> using namespace std; typedef long long ll; const int maxn=200010; ll s[maxn]; int k,m,n; ll p; int powermod(int x,int n) { int res=1; while(n>0) { if(n&1) res=(res*x); x=x*x; n=n>>1; } return res; } int main() { ios::sync_with_stdio(false); while(cin>>k>>m>>n>>p) { ll ans=0; for(int i = 1; i <= k; i++) cin>>s[i]; sort(s+1,s+k+1); ll S = (powermod(n, m)-n)/(n-1); for(int i = 1; i <= S; i++) { s[i] = (s[i] + s[(i-1)/n]) % p; ans = (ans + s[i]) % p; } cout<<ans<<endl; } return 0; }
