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;
}