POJ 1797 Heavy Transportation

Heavy Transportation

Time Limit: 3000MS		Memory Limit: 30000K
Total Submissions: 9836		Accepted: 2665

Description

Background
Hugo Heavy is happy. After the breakdown of the Cargolifter project he can now expand business. But he needs a clever man who tells him whether there really is a way from the place his customer has build his giant steel crane to the place where it is needed on which all streets can carry the weight.
Fortunately he already has a plan of the city with all streets and bridges and all the allowed weights.Unfortunately he has no idea how to find the the maximum weight capacity in order to tell his customer how heavy the crane may become. But you surely know.

Problem
You are given the plan of the city, described by the streets (with weight limits) between the crossings, which are numbered from 1 to n. Your task is to find the maximum weight that can be transported from crossing 1 (Hugo's place) to crossing n (the customer's place). You may assume that there is at least one path. All streets can be travelled in both directions.

Input

The first line contains the number of scenarios (city plans). For each city the number n of street crossings (1 <= n <= 1000) and number m of streets are given on the first line. The following m lines contain triples of integers specifying start and end crossing of the street and the maximum allowed weight, which is positive and not larger than 1000000. There will be at most one street between each pair of crossings.

Output

The output for every scenario begins with a line containing "Scenario #i:", where i is the number of the scenario starting at 1. Then print a single line containing the maximum allowed weight that Hugo can transport to the customer. Terminate the output for the scenario with a blank line.

Sample Input

1
3 3
1 2 3
1 3 4
2 3 5

Sample Output

Scenario #1:
4

Source

TUD Programming Contest 2004, Darmstadt, Germany

 

 

就是求最大生成树的最小边

WA了好多次，因为输出格式的那个冒号丢了。。。。

接着还有就是那个判断成立的条件，只有当1和N在同一个集合里才叫做完成，而不是1和N都出现过

注意输出和上面这一点，就能马上过了

#include<cstdio>
#include<cstring>
#include<algorithm>
const int E=1001*1001+10;
const int V=1010;
using namespace std;
int n,m;
int p[V];
struct EDGE
{
    int x,y,v;
} edge[E*2];

bool cmp(EDGE a,EDGE b)
{
    return a.v>b.v;
}

int getfather(int a)
{
    if(a!=p[a]) p[a]=getfather(p[a]);
    return p[a];
}

void Union(int a,int b)
{
    a=getfather(a);
    b=getfather(b);
    p[a]=b;
}
int main()
{
    int T;
    scanf("%d",&T);
    int cas=1;
    while(T--)
    {
        scanf("%d%d",&n,&m);
        for(int i=1; i<=n; i++)  p[i]=i;
        for(int i=0; i<m; i++)
        {
            scanf("%d%d%d",&edge[i].x,&edge[i].y,&edge[i].v);
        }
        sort(edge,edge+m,cmp);
        bool f1=false,f2=false;
        for(int i=0; i<m; i++)
        {
            int a=getfather(edge[i].x);
            int b=getfather(edge[i].y);
            if(a!=b)
            {
                Union(edge[i].x,edge[i].y);
            }
            a=getfather(1);
            b=getfather(n);
            if(a==b)
            {
                printf("Scenario #%d:/n",cas++);
                printf("%d/n",edge[i].v);
                printf("/n");
                break;
            }
        }
    }
    return 0;
}