MST:Agri-Net(POJ 1258)
题目大意:农夫有一片农场,现在他要把这些田地用管子连起来,田地之间有一定距离,铺设每一段管子的长度与这些田地与田地距离是一样的,问你最小的铺设方案。
这一题很裸,Kruskal算法即可,不过一定要注意,这一题是多组数据输入,边的总数记得初始化!
1 #include <iostream> 2 #include <functional> 3 #include <algorithm> 4 #define MAX 12100 5 #define MAX_N 110 6 7 using namespace std; 8 9 typedef int Position; 10 typedef struct _edge 11 { 12 int cost; 13 Position to; 14 Position from; 15 }Edge_Set; 16 int fcomp(const void *a, const void *b) 17 { 18 return (*(Edge_Set *)a).cost - (*(Edge_Set *)b).cost; 19 } 20 21 static Edge_Set edge[MAX * 2]; 22 static Position Set[MAX_N]; 23 24 void Kruskal(const int, const int); 25 Position Find(Position); 26 bool If_Same(Position, Position); 27 void Union(Position, Position); 28 29 int main(void) 30 { 31 int N, e_sum, tmp; 32 while (~scanf("%d", &N)) 33 { 34 e_sum = 0; 35 for (int i = 0; i < N; i++) 36 { 37 for (int j = 0; j < N; j++) 38 { 39 scanf("%d", &tmp); 40 if (i == j) continue; 41 edge[e_sum].from = i, edge[e_sum].to = j; edge[e_sum++].cost = tmp; 42 } 43 } 44 Kruskal(e_sum, N); 45 } 46 return 0; 47 } 48 49 Position Find(Position x) 50 { 51 if (Set[x] < 0) 52 return x; 53 else return Set[x] = Find(Set[x]); 54 } 55 56 bool If_Same(Position x, Position y) 57 { 58 Position px, py; 59 px = Find(x); py = Find(y); 60 return px == py; 61 } 62 63 void Union(Position x, Position y) 64 { 65 Position px, py; 66 px = Find(x); py = Find(y); 67 68 if (px != py) 69 { 70 if (Set[px] < Set[py]) 71 { 72 Set[px] += Set[py]; 73 Set[py] = px; 74 } 75 else 76 { 77 Set[py] += Set[px]; 78 Set[px] = py; 79 } 80 } 81 } 82 83 void Kruskal(const int R_sum, const int Node_sum) 84 { 85 fill(Set, Set + Node_sum, -1); 86 qsort(edge, R_sum, sizeof(Edge_Set), fcomp); 87 88 Edge_Set e; 89 long long ans = 0; 90 91 for (int i = 0; i < R_sum; i++) 92 { 93 e = edge[i]; 94 if (!If_Same(e.from, e.to)) 95 { 96 Union(e.from, e.to); 97 ans += e.cost; 98 } 99 } 100 printf("%lld\n", ans); 101 }