POJ1861 Network Kruscal+并查集 C语言
题目：http://poj.org/problem?id=1861
题目大意：要用最短的电缆把所有的电脑都连接起来。
算法：Kruscal+并查集
思路：常规Kruscal+并查集。先开始没注意到是SPJ，看样例输出一个环很是疑惑，纠结了半天，看了discuss，才知道是样例的问题……不用管样例，常规做就好
提交情况：1次AC
View Code
1 #include <cstdio>
2
3 #include <cstdlib>
4
5 #include <cstring>
6
7 #include <algorithm>
8
9 using namespace std;
10
11
12
13 #define MAXN 20000
14
15 #define MAX 1100
16
17
18
19 typedef struct Graph {
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21 int u, v, len;
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23 }graph;
24
25
26
27 graph edge[MAXN], tree[MAX];
28
29 int father[MAX];
30
31
32
33 void Build_Map(int n, int m) {
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35 int i, j;
36
37 for(i = 1; i <= m; i++)
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39 scanf("%d%d%d", &edge[i].u, &edge[i].v, &edge[i].len);
40
41 for(j = 1; j <= n; j++)
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43 father[j] = j;
44
45 }
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47
48
49 int cmp (graph &a, graph &b) {
50
51 return a.len < b.len;
52
53 }
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55
56
57 int Find(int u) {
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59 return u != father[u] ? Find(father[u]) : father[u];
60
61 }
62
63
64
65 void Union(int u, int v){
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67 father[u] = v;
68
69 }
70
71
72
73 int MLT(int m) {
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75 int max = 0;
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77 int i, j = 1;
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79 int fu, fv;
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81 for(i = 1; i <= m; i++) {
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83 fu = Find(edge[i].u);
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85 fv = Find(edge[i].v);
86
87 if (fu != fv) {
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89 max = max > edge[i].len ? max : edge[i].len;
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91 tree[j].u = edge[i].u;
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93 tree[j++].v = edge[i].v;
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95 Union(fu, fv);
96
97 }
98
99 }
100
101 return max;
102
103 }
104
105
106
107 void Print(int n) {
108
109 int i;
110
111 printf("%d\n", n - 1);
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113 for(i = 1; i < n; i++)
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115 printf("%d %d\n", tree[i].u, tree[i].v);
116
117 }
118
119
120
121 int main() {
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123 int n, m;
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125 scanf("%d%d", &n, &m);
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127 Build_Map(n, m);
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129 sort(edge + 1, edge + m + 1, cmp);
130
131 printf("%d\n", MLT(m));
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133 Print(n);
134
135 //system("pause");
136
137 return 0;
138
139 }
140
141
142
