hdu_2236

 1 // hdu2236

 2 // Graph Match  binary search + enumeration + bipartite

 3 // Dec.26 2014

 4 

 5 #include <cstdio>

 6 #include <cstring>

 7 #include <algorithm>

 8 

 9 #define MaxN 111

10 #define ACCEPT

11 

12 int G[MaxN][MaxN], T, n, max_edge, min_edge, l, r, mid, enum_edge, gx[MaxN], gy[MaxN];

13 bool vis[MaxN], is_match;

14 

15 bool dfs(int u)

16 {

17     for(int i = 1; i <= n; ++i){

18         if(G[u][i] >= enum_edge && G[u][i] <= enum_edge + mid && vis[i] == false){

19             vis[i] = true;

20             if(gy[i] == -1 || dfs(gy[i]) == true){

21                 gy[i] = u;

22                 gx[u] = i;

23                 return true;

24             }

25         }

26     }

27     return false;

28 }

29 

30 bool hungry()

31 {

32     memset(gx, -1, sizeof(gx));

33     memset(gy, -1, sizeof(gy));

34     for(int i = 1; i <= n; ++i){

35         memset(vis, false, sizeof(vis));

36         if(dfs(i) == false)

37             return false;

38     }

39 }

40 

41 int main(int argc, char const *argv[])

42 {

43     #ifndef ACCEPT

44         freopen("in.txt","r",stdin);

45     #endif

46     scanf("%d", &T);

47     while(T--){

48         // input , get the max num and min num

49         max_edge = -1;

50         min_edge = 101;

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

52         for(int i = 1; i <= n; ++i){

53             for(int j = 1; j <= n; ++j){

54                 scanf("%d", &G[i][j]);

55                 max_edge = std::max(G[i][j], max_edge);

56                 min_edge = std::min(G[i][j], min_edge);

57             }

58         }

59         // 

60         l = 0;

61         r = max_edge - min_edge;

62         while(true){

63             mid  = (l + r) >> 1;

64             is_match = false;

65             for(enum_edge = min_edge; enum_edge + mid <= max_edge; ++enum_edge){

66                 if(hungry() == true){

67                     is_match = true;

68                     break;

69                 }

70             }

71             if(is_match == true)

72                 r = mid;

73             if(l == mid)

74                 break;

75             if(is_match == false)

76                 l = mid;

77         }

78         printf("%d\n", r);

79     }

80     return 0;

81 }