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。
1 /* 2 ━━━━━┒ギリギリ♂ eye！ 3 ┓┏┓┏┓┃キリキリ♂ mind！ 4 ┛┗┛┗┛┃＼○／ 5 ┓┏┓┏┓┃ / 6 ┛┗┛┗┛┃ノ) 7 ┓┏┓┏┓┃ 8 ┛┗┛┗┛┃ 9 ┓┏┓┏┓┃ 10 ┛┗┛┗┛┃ 11 ┓┏┓┏┓┃ 12 ┛┗┛┗┛┃ 13 ┓┏┓┏┓┃ 14 ┃┃┃┃┃┃ 15 ┻┻┻┻┻┻ 16 */ 17 #include <algorithm> 18 #include <iostream> 19 #include <iomanip> 20 #include <cstring> 21 #include <climits> 22 #include <complex> 23 #include <fstream> 24 #include <cassert> 25 #include <cstdio> 26 #include <bitset> 27 #include <vector> 28 #include <deque> 29 #include <queue> 30 #include <stack> 31 #include <ctime> 32 #include <set> 33 #include <map> 34 #include <cmath> 35 using namespace std; 36 #define fr first 37 #define sc second 38 #define cl clear 39 #define BUG puts("here!!!") 40 #define W(a) while(a--) 41 #define pb(a) push_back(a) 42 #define Rint(a) scanf("%d", &a) 43 #define Rll(a) scanf("%lld", &a) 44 #define Rs(a) scanf("%s", a) 45 #define Cin(a) cin >> a 46 #define FRead() freopen("in", "r", stdin) 47 #define FWrite() freopen("out", "w", stdout) 48 #define Rep(i, len) for(int i = 0; i < (len); i++) 49 #define For(i, a, len) for(int i = (a); i < (len); i++) 50 #define Cls(a) memset((a), 0, sizeof(a)) 51 #define Clr(a, x) memset((a), (x), sizeof(a)) 52 #define Full(a) memset((a), 0x7f7f, sizeof(a)) 53 #define lrt rt << 1 54 #define rrt rt << 1 | 1 55 #define pi 3.14159265359 56 #define RT return 57 #define lowbit(x) x & (-x) 58 #define onenum(x) __builtin_popcount(x) 59 typedef long long LL; 60 typedef long double LD; 61 typedef unsigned long long ULL; 62 typedef pair<int, int> pii; 63 typedef pair<string, int> psi; 64 typedef map<string, int> msi; 65 typedef vector<int> vi; 66 typedef vector<LL> vl; 67 typedef vector<vl> vvl; 68 typedef vector<bool> vb; 69 70 typedef struct Edge { 71 int u, v, w; 72 Edge() {} 73 Edge(int uu, int vv, int ww) : u(uu), v(vv), w(ww) {} 74 }Edge; 75 const int maxn = 1010; 76 const int maxm = 20020; 77 int n, m; 78 int pre[maxn]; 79 Edge edge[maxm]; 80 81 bool cmp(Edge a, Edge b) { 82 RT a.w > b.w; 83 } 84 85 int find(int x) { 86 return x == pre[x] ? x : pre[x] = find(pre[x]); 87 } 88 89 int unite(int x, int y) { 90 int fx = find(x); 91 int fy = find(y); 92 if(fx != fy) { 93 pre[fy] = fx; 94 return 1; 95 } 96 return 0; 97 } 98 99 int main() { 100 // FRead(); 101 int u, v, c; 102 while(~Rint(n) && ~Rint(m)) { 103 Rep(i, n+5) pre[i] = i; 104 Rep(i, m) { 105 Rint(u); Rint(v); Rint(c); 106 edge[i] = Edge(u, v, c); 107 } 108 sort(edge, edge+m, cmp); 109 int ret = 0; 110 Rep(i, m) { 111 if(unite(edge[i].u, edge[i].v)) { 112 ret += edge[i].w; 113 } 114 } 115 int flag = 0; 116 For(i, 1, n+1) { 117 if(pre[i] == i) flag++; 118 if(flag > 1) break; 119 } 120 if(flag > 1) printf("-1 "); 121 else printf("%d ", ret); 122 } 123 RT 0; 124 }