Submission #840461

#TimeUsernameProblemLanguageResultExecution timeMemory
840461TheLostCookieClosing Time (IOI23_closing)C++17
83 / 100
179 ms31832 KiB
#include "closing.h" #include <algorithm> #include <functional> #include <vector> int max_score(int N, int X, int Y, long long int K, std::vector<int> U, std::vector<int> V, std::vector<int> W) { std::vector<std::vector<std::pair<int,long long int>>> adj(N); for(int i = 0; i < N-1; i++) { adj[U[i]].emplace_back(V[i],W[i]); adj[V[i]].emplace_back(U[i],W[i]); } std::vector<long long int> dX(N), dY(N); auto dfs = [&](auto &&self, std::vector<long long int> &d, int u, int p)->void{ for(auto [v,w]: adj[u]) { if(v != p) { d[v] = d[u]+w; self(self,d,v,u); } } return; }; dfs(dfs,dX,X,-1); dfs(dfs,dY,Y,-1); int ans = 0; //Case: No overlap { std::vector<long long int> d(dX); d.reserve(2*N); for(int i = 0; i < N; i++) { d.push_back(dY[i]); } std::sort(d.begin(),d.end()); long long int sum = 0; while(ans<2*N && sum+d[ans]<=K) sum+=d[ans++]; } //Case: XY bridge { std::vector<long long int> freeChoices; std::vector<std::pair<long long int,long long int>> pairChoices; long long int xy = 0; int xyLen = 0; for(int i = 0; i < N; i++) { long long int d0 = std::min(dX[i],dY[i]); long long int d1 = std::max(dX[i],dY[i]); if(d0+d1 == dX[Y]) { xy += d0; xyLen++; freeChoices.push_back(d1-d0); } else if(d0 <= d1-d0) { freeChoices.push_back(d0); freeChoices.push_back(d1-d0); } else { pairChoices.emplace_back(d0,d1-d0); } } std::sort(freeChoices.begin(), freeChoices.end()); for(int i = 0; i < int(freeChoices.size())-1; i++) { freeChoices[i+1] += freeChoices[i]; } auto tryCase = [&](long long int d) { long long int k = K-xy-d; if(k<0) return -2*N; //Invalid case int ret = (std::upper_bound(freeChoices.begin(),freeChoices.end(),k)-freeChoices.begin()); return ret; }; std::sort(pairChoices.begin(), pairChoices.end(),[](std::pair<int,int> a, std::pair<int,int> b){return a.first+a.second<b.first+b.second;}); int pn = pairChoices.size(); if(pn == 0) { ans = std::max(ans,xyLen+tryCase(0)); } else { std::vector<long long int> prefMax(pn), suffMin(pn); prefMax[0] = pairChoices[0].second; for(int i = 1; i < pn; i++) { prefMax[i] = std::max(prefMax[i-1],pairChoices[i].second); } suffMin[pn-1] = pairChoices[pn-1].first; for(int i = pn-2; i >= 0; i--) { suffMin[i] = std::min(suffMin[i+1],pairChoices[i].first); } long long int prefPairs = 0; for(int i = 0; i <= pn; i++) { //Case: i of the pairs are chosen. ans = std::max(ans,xyLen+2*i+tryCase(prefPairs)); //Case: i of the pairs less one are chosen if(i) { ans = std::max(ans,xyLen+2*i-1+tryCase(prefPairs-prefMax[i-1])); } //Case: i of the pairs more one are chosen if(i != pn) { ans = std::max(ans,xyLen+2*i+1+tryCase(prefPairs+suffMin[i])); prefPairs += (pairChoices[i].first+pairChoices[i].second); } } } } return ans; }
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