POJ 2075

#include<iostream>
#include<stdio.h>
#include<string>
#include<map>
#include<iomanip>
#define MAXN 500
#define inf 1000000000
typedef double elem_t;
using namespace std;

double _m[MAXN][MAXN];
int pre[MAXN];
map<string,int> coll;
map<string,int>::iterator pos1,pos2;

elem_t prim(int n,elem_t mat[][MAXN],int* pre){
    elem_t min[MAXN],ret=0;
    int v[MAXN],i,j,k;
    for (i=0;i<n;i++)
        min[i]=inf,v[i]=0,pre[i]=-1;
    for (min[j=0]=0;j<n;j++){
        for (k=-1,i=0;i<n;i++)
            if (!v[i]&&(k==-1||min[i]<min[k]))
                k=i;
        for (v[k]=1,ret+=min[k],i=0;i<n;i++)
            if (!v[i]&&mat[k][i]<min[i])
                min[i]=mat[pre[i]=k][i];
    }
    return ret;
}

int main()
{
    //freopen("acm.acm","r",stdin);
    double st;
    int i;
    int j;
    double ans;
    int num_name;
    int edge;
    string s;
    string s1;
    double len;
    for(i = 0; i < MAXN ; ++ i)
    {
        for(j = 0; j < MAXN; ++ j)
            _m[i][j] = inf;
    }
    cin>>st;
    cin>>num_name;
    for(i = 0; i < num_name; ++ i)
    {
        cin>>s;
        coll.insert(pair<string,int>(s,i));
    }
    cin>>edge;
    for(i = 0; i < edge; ++ i)
    {
        cin>>s;
        cin>>s1;
        cin>>len;
        pos1 = coll.find(s);
        pos2 = coll.find(s1);
        _m[pos1->second][pos2->second] = len;
        _m[pos2->second][pos1->second] = len;
    }
    if((ans = prim(num_name,_m,pre)) > st)
        cout<<"Not enough cable "<<endl;
    else
        cout<<"Need "<<setiosflags(ios::fixed)<<setprecision(1)<<ans<<" miles of cable"<<endl;
}