[POJ2377]Bad Cowtractors(最大生成树，Kruskal)

题目链接：http://poj.org/problem?id=2377

于是就找了一道最大生成树的AC了一下，注意不连通的情况啊，WA了一次。

 /*

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 */

 #include <algorithm>

 #include <iostream>

 #include <iomanip>

 #include <cstring>

 #include <climits>

 #include <complex>

 #include <fstream>

 #include <cassert>

 #include <cstdio>

 #include <bitset>

 #include <vector>

 #include <deque>

 #include <queue>

 #include <stack>

 #include <ctime>

 #include <set>

 #include <map>

 #include <cmath>

 using namespace std;

 #define fr first

 #define sc second

 #define cl clear

 #define BUG puts("here!!!")

 #define W(a) while(a--)

 #define pb(a) push_back(a)

 #define Rint(a) scanf("%d", &a)

 #define Rll(a) scanf("%lld", &a)

 #define Rs(a) scanf("%s", a)

 #define Cin(a) cin >> a

 #define FRead() freopen("in", "r", stdin)

 #define FWrite() freopen("out", "w", stdout)

 #define Rep(i, len) for(int i = 0; i < (len); i++)

 #define For(i, a, len) for(int i = (a); i < (len); i++)

 #define Cls(a) memset((a), 0, sizeof(a))

 #define Clr(a, x) memset((a), (x), sizeof(a))

 #define Full(a) memset((a), 0x7f7f, sizeof(a))

 #define lrt rt << 1

 #define rrt rt << 1 | 1

 #define pi 3.14159265359

 #define RT return

 #define lowbit(x) x & (-x)

 #define onenum(x) __builtin_popcount(x)

 typedef long long LL;

 typedef long double LD;

 typedef unsigned long long ULL;

 typedef pair<int, int> pii;

 typedef pair<string, int> psi;

 typedef map<string, int> msi;

 typedef vector<int> vi;

 typedef vector<LL> vl;

 typedef vector<vl> vvl;

 typedef vector<bool> vb;

 typedef struct Edge {

     int u, v, w;

     Edge() {}

     Edge(int uu, int vv, int ww) : u(uu), v(vv), w(ww) {}

 }Edge;

 const int maxn = ;

 const int maxm = ;

 int n, m;

 int pre[maxn];

 Edge edge[maxm];

 bool cmp(Edge a, Edge b) {

     RT a.w > b.w;

 }

 int find(int x) {

     return x == pre[x] ? x : pre[x] = find(pre[x]);

 }

 int unite(int x, int y) {

     int fx = find(x);

     int fy = find(y);

     if(fx != fy) {

         pre[fy] = fx;

         return ;

     }

     return ;

 }

 int main() {

     // FRead();

     int u, v, c;

     while(~Rint(n) && ~Rint(m)) {

         Rep(i, n+) pre[i] = i;

         Rep(i, m) {

             Rint(u); Rint(v); Rint(c);

             edge[i] = Edge(u, v, c);

         }

         sort(edge, edge+m, cmp);

         int ret = ;

         Rep(i, m) {

             if(unite(edge[i].u, edge[i].v)) {

                 ret += edge[i].w;

             }

         }

         int flag = ;

         For(i, , n+) {

             if(pre[i] == i) flag++;

             if(flag > ) break;

         }

         if(flag > ) printf("-1\n");

         else printf("%d\n", ret);

     }

     RT ;

 }