poj 2485 Highways

用kruskal（）算法处理》》。

 1 #include<stdio.h>

 2 #include<stdlib.h>

 3 #define MAXN 300000

 4 

 5 int T, n, h, u[MAXN], v[MAXN], w[MAXN], p[510], r[MAXN];

 6 

 7 int cmp(const void *_p, const void *_q)

 8 {

 9     int *p = (int *)_p;

10     int *q = (int *)_q;

11     return w[*p] - w[*q];

12 }

13 

14 int find(int x){return p[x] == x ? x : p[x] = find(p[x]);}

15 

16 void kruskal()

17 {

18     int ans = 0;

19     for(int i = 0; i < n; i ++) p[i] = i;

20     for(int i = 0; i < h; i ++) r[i] = i;

21     qsort(r,h,sizeof(r[0]),cmp);

22     for(int i = 0; i < h; i ++)

23     {

24         int e = r[i], x = find(u[e]), y = find(v[e]);

25         if(x != y){ans = w[e]; p[x] = y;}

26     }

27     printf("%d\n",ans);

28 }

29 

30 int main()

31 {

32     while(~scanf("%d",&T))

33     {

34         while(T--)

35         {

36             scanf("%d",&n);

37             h = 0;

38             for(int i = 0; i < n; i ++)

39             {

40                 for(int j = 0; j < n; j ++)

41                 {

42                     int a;

43                     scanf("%d",&a);

44                     if(i == j) continue;

45                     u[h] = i, v[h] = j, w[h++] = a;

46                 }

47             }

48             kruskal();

49         }

50     }    

51 }