Sweet Butter USACO 3.2
用n次djikstra 求最小和的思路，关键是如何优化,开始直接用数组存,case8 就过不去了,后来把extract-min换成
priority_queue 到case9还是没过去。
先贴个我的 ，在贴个大牛的
/* ID: hubiao cave PROG: butter LANG: C++ */ #include<iostream> #include<fstream> #include<cstring> #include<queue> using namespace std; #define INFINITE 888888 int N,P,C; int djistra(int origial); int visit[801]; int counter[801]; int pastures[801][801]; struct mycom { bool operator()(pair<int,int>p1,pair<int,int>p2) { if(p1.first!=p2.first) return p1.first>p2.first; else { return p1.second>p2.second; } } }; int main() { ifstream fin("butter.in"); ofstream fout("butter.out"); int index; int start,end,value; fin>>N>>P>>C; for(int i=0;i<N;i++) { fin>>index; counter[index]++; } for(int i=1;i<=P;i++) for(int j=1;j<=P;j++) { if(i==j) pastures[i][j]=0; else pastures[i][j]=INFINITE; } for(int i=0;i<C;i++) { fin>>start>>end>>value; pastures[start][end]=pastures[end][start]=value; } int minimum=INFINITE; for(int i=1;i<=P;i++) { int temp=djistra(i); if(minimum>temp) minimum=temp; } fout<<minimum<<endl; return 0; } int djistra(int original) { priority_queue<pair<int,int> ,vector<pair<int,int> > ,mycom> myheap; int sum=0; int weight[801]; for(int i=1;i<=P;i++) { //weight[i]=pastures[original][i]; weight[i]=INFINITE; //myheap.push(make_pair(pastures[original][i],i)); } weight[original]=0; myheap.push(make_pair(pastures[original][original],original)); memset(visit,0,801*4); bool flag=true; while(!myheap.empty()) { int marki=1; int value; //for(int i=1;i<=P;i++) //{ //if(mini>weight[i]&&!visit[i]) //{ //marki=i; // pair<int, int> p=myheap.top(); myheap.pop(); marki=p.second; value=p.first; if(!visit[marki]) { //} visit[marki]=1; for(int i=1;i<=P;i++) { if(value+pastures[marki][i]<weight[i]) { weight[i]=value+pastures[marki][i]; myheap.push(make_pair(weight[i],i)); } } } // flag=0; //for(int i=1;i<=P;i++) // if(!visit[i]) //flag=1; } for(int i=1;i<=P;i++) { sum+=counter[i]*weight[i]; } return sum; }
#include <iostream> #include <fstream> #include <cstdlib> #include <queue> using namespace std; struct vertex { int dist; bool known; } v[801]; int nCow, nPastures, nEdge; int cow[503]; const int INF = 0x7FFFF; // edge vector < int >Map[801]; vector < int >val[801]; int dijkstra(int start) { for (int i = 1; i <= nPastures; i++) { v[i].dist = INF; v[i].known = false; } priority_queue < pair < int, int > >heap; heap.push(make_pair(0, start)); v[start].dist = 0; int u, w, cost; while (!heap.empty()) { u = heap.top().second; //cout << u << endl; heap.pop(); if (!v[u].known) { v[u].known = true; for (unsigned int i = 0; i < Map[u].size(); i++) { w = Map[u][i]; if (!v[w].known) cost = val[u][i]; if (v[w].dist > v[u].dist + cost) { v[w].dist = v[u].dist + cost; heap.push(make_pair(-v[w].dist, w)); } } } } int totalDist = 0; for (int j = 0; j <= nCow; j++) totalDist += v[cow[j]].dist; //cout << start << ' ' << totalDist << endl; return totalDist; } int main() { ifstream fin("butter.in"); ofstream fout("butter.out"); fin >> nCow >> nPastures >> nEdge; for (int i = 0; i < nCow; i++) fin >> cow[i]; int l, r, d; for (int i = 0; i < nEdge; i++) { fin >> l >> r >> d; Map[l].push_back(r); Map[r].push_back(l); val[l].push_back(d); val[r].push_back(d); } int min = INF, walkDist; for (int i = 1; i <= nPastures; i++) { walkDist = dijkstra(i); if (min > walkDist) min = walkDist; } cout << min << endl; fout << min << endl; fin.close(); fout.close(); return 0; }
我改过之后的
/* ID: hubiao cave PROG: butter LANG: C++ */ #include<iostream> #include<fstream> #include<cstring> #include<queue> #include<vector> using namespace std; #define INFINITE 888888 int N,P,C; int djistra(int origial); int visit[801]; int counter[801]; int pastures[801][801]; vector<int> gmaps[801]; vector<int> gvalues[801]; struct mycom { bool operator()(pair<int,int>p1,pair<int,int>p2) { if(p1.first!=p2.first) return p1.first>p2.first; else { return p1.second>p2.second; } } }; int main() { ifstream fin("butter.in"); ofstream fout("butter.out"); int index; int start,end,value; fin>>N>>P>>C; for(int i=0;i<N;i++) { fin>>index; counter[index]++; } for(int i=1;i<=P;i++) for(int j=1;j<=P;j++) { if(i==j) pastures[i][j]=0; else pastures[i][j]=INFINITE; } for(int i=0;i<C;i++) { fin>>start>>end>>value; //pastures[start][end]=pastures[end][start]=value; gmaps[start].push_back(end); gmaps[end].push_back(start); gvalues[start].push_back(value); gvalues[end].push_back(value); } int minimum=INFINITE; for(int i=1;i<=P;i++) { int temp=djistra(i); if(minimum>temp) minimum=temp; } fout<<minimum<<endl; return 0; } int djistra(int original) { priority_queue<pair<int,int> ,vector<pair<int,int> > ,mycom> myheap; int sum=0; int weight[801]; for(int i=1;i<=P;i++) { //weight[i]=pastures[original][i]; weight[i]=INFINITE; //myheap.push(make_pair(pastures[original][i],i)); } weight[original]=0; myheap.push(make_pair(pastures[original][original],original)); memset(visit,0,801*4); // bool flag=true; while(!myheap.empty()) { int marki=1; int value; //for(int i=1;i<=P;i++) //{ //if(mini>weight[i]&&!visit[i]) //{ //marki=i; // pair<int, int> p=myheap.top(); myheap.pop(); marki=p.second; value=p.first; if(!visit[marki]) { //} visit[marki]=1; //for(int i=1;i<=P;i++) for(int i=0;i<gmaps[marki].size();i++) { int w=gmaps[marki][i]; //if(value+pastures[marki][i]<weight[i]) if(value+gvalues[marki][i]<weight[w]) { weight[w]=value+gvalues[marki][i]; myheap.push(make_pair(weight[w],w)); } } } // flag=0; //for(int i=1;i<=P;i++) // if(!visit[i]) //flag=1; } for(int i=1;i<=P;i++) { sum+=counter[i]*weight[i]; } return sum; }
