online_judge_1024

#include <iostream>#include <algorithm>using namespace std;const int N = 101;struct Edge{    int a,b;    int cost;    bool operator < (const Edge &A) const    {        return cost < A.cost;    }}edge[N];int Tree[N];int findRoot(int x){    if(Tree[x] == -1)        return x;    int tmp,ret;    tmp = x;    while(Tree[x] != -1)    {        x = Tree[x];    }    ret = x;    x = tmp;    while(Tree[x] != -1)    {        tmp = Tree[x];        Tree[x] = ret;        x = tmp;    }    return ret;}int main(){    int n,m;    int i,s,e;    int result;    while(cin>>n>>m)    {        if(n == 0)            break;        for(i=1; i<=n; ++i)        {            cin>>edge[i].a>>edge[i].b>>edge[i].cost;        }        for(i=1; i<=m; ++i)        {            Tree[i] = -1;        }        result = 0;        sort(edge+1, edge+n+1);        for(i=1; i<=n; ++i)        {            s = findRoot(edge[i].a);            e = findRoot(edge[i].b);            if(s != e)            {                Tree[s] = e;                result += edge[i].cost;            }        }        s = 0;        for(i=1; i<=m; ++i)        {            if(Tree[i] == -1)                s++;        }        if(s>1)            cout<<"?"<<endl;        else            cout<<result<<endl;    }    return 0;}

看花容易绣花难，看似简单的题目，做起来也费神。花了近半小时……缺乏锻炼呀！