【并查集+枚举】杭电 hdu 1598 find the most comfortable road

/* THE PROGRAM IS MADE BY PYY */
/*----------------------------------------------------------------------------//
    Copyright (c) 2011 panyanyany All rights reserved.

    URL   : http://acm.hdu.edu.cn/showproblem.php?pid=1598
    Name  : 1598 find the most comfortable road

    Date  : Monday, January 23, 2012
    Time Stage : 2.5 hours

    Result: 
5287995	2012-01-23 16:23:56	Accepted	1598
265MS	220K	1916 B
C++	pyy


Test Data :

Review :
枚举+并查集。
这题放在最短路的专题里，最短路实在不会，只好百度一下了。
牛人解题报告：
http://www.cnblogs.com/mrlai/archive/2011/03/31/2001405.html
http://blog.csdn.net/zxddavy/article/details/6612324
//----------------------------------------------------------------------------*/

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           using namespace std ; #define INF (-1) #define MAXN 1002 typedef __int64 LL ; #define min(x, y) ((x) < (y) ? (x) : (y)) #define max(x, y) ((x) > (y) ? (x) : (y)) #define MEM(a, v) memset (a, v, sizeof (a)) struct SARS { int s, e, c ; bool operator< (const SARS &s) { return c < s.c ; } }; bool used[MAXN] ; int n, m, q ; int set[MAXN] ; SARS map[MAXN] ; int find (int x) { while (set[x] != x) x = set[x] ; return x ; } int main () { int i, j ; int x, y, c ; int res ; while (~scanf ("%d%d", &n, &m)) { MEM (map, INF) ; for (i = 0 ; i < m ; ++i) { scanf ("%d%d%d", &map[i].s, &map[i].e , &map[i].c) ; } sort (map, map+m) ; scanf ("%d", &q) ; while (q--) { scanf ("%d%d", &x, &y) ; res = INF ; for (i = m-1 ; i >= 0 ; --i) { for (j = 0 ; j < m ; ++j) set[j] = j ; for (j = i ; j >= 0 ; --j) { int xx = find (map[j].s) ; int yy = find (map[j].e) ; if (xx != yy) set[xx] = set[yy] ; if (find (x) == find (y)) { if (res == INF || res > map[i].c - map[j].c) { res = map[i].c - map[j].c ; } break ; } } } printf ("%d\n", res) ; } } return 0 ; }