Kruskal HDOJ 1863 畅通工程

 

题目传送门

 1 /*  2  此题为：HDOJ 1233 + HDOJ 1232  3 */  4 #include <cstdio>  5 #include <algorithm>  6 #include <cstring>  7 #include <cmath>  8 using namespace std;  9 10 const int MAX_N = 100 + 10; 11 int pre[MAX_N]; 12 int tot; 13 int sum; 14 struct NODE 15 { 16 int x, y; 17 int len; 18 }node[MAX_N]; 19 20 int find(int root) 21 { 22 int son, tmp; 23 son = root; 24 25 while (root != pre[root]) 26  { 27 root = pre[root]; 28  } 29 while (son != root) 30  { 31 tmp = pre[son]; 32 pre[son] = root; 33 son = tmp; 34  } 35 36 return root; 37 } 38 39 bool cmp(NODE a, NODE b) 40 { 41 return a.len < b.len; 42 } 43 44 int main(void) //HDOJ 1863 畅通工程 45 { 46 //freopen ("inC.txt", "r", stdin); 47 int n, m; //n路， m村庄 48 49 while (~scanf ("%d%d", &n, &m) && n) 50  { 51 tot = m - 1; 52 for (int i=1; i<=m; ++i) 53  { 54 pre[i] = i; 55  } 56 for (int i=1; i<=n; ++i) 57  { 58 scanf ("%d%d%d", &node[i].x, &node[i].y, &node[i].len); 59  } 60 sort (node+1, node+1+n, cmp); 61 sum = 0; 62 for (int i=1; i<=n; ++i) 63  { 64 int a, b; 65 a = find (node[i].x); 66 b = find (node[i].y); 67 if (a != b) 68  { 69 pre[a] = b; 70 sum += node[i].len; 71 --tot; 72  } 73  } 74 if (tot == 0) 75 printf ("%d\n", sum); 76 else 77 puts ("?"); 78  } 79 }