1082  Addingthemaximumflow arc
Time Limit : 2 Second
Memory Limit : 128 MB
Submission: 300
Solved: 76
 Description
 In the network G(s, t, N, A, U)(s: the souce node, t: the sink node, N: the set of the nodes, A: the set of the arcs, U: the set of the capacity of the arcs), adding a arc's capacity with one unit may make the maximum flow larger. We call this arc as the addingthemaximumflow arc.
Now the problem is that giving a network G, you must calculate the number of the the addingthemaximumflow arcs in the network G.  Input
 The first line of the input contains an integer T, giving the number of the test cases.
For each test case: The first line contains four integers: n, m, s and t(0 < n <= 400, 0 < m <= 10000, 0 < s, t <= n), giving the number of nodes, the number of arcs, the source node and the sink node.
And there are m lines followed: each line describe an arc: a, b, c, the arc is from a to b and its capacity is c(0 < a, b <= n, 0 < c < 1000).  Output
 For each test case, the output contains a single integer which is the number of the addingthemaximum flow arcs.
 sample input

1 4 4 1 4 1 2 3 1 3 5 2 4 2 3 4 6
 sample output

2
 hint
 There may be multiarcs in the network, that is to say there may be more than one arc between two nodes.
 source
 Liu sh