思路分析：
因为流向是一定的，所以直接把每个结点的val流动看成最后一个流动的val。 主要还是熟悉一下如何写CLASS。
代码：
#include <iostream>
#include <vector>
#include <queue>
using namespace std
;
struct node
{
vector
<int>u
;
int val
, in_degree
;
node() {
val
= in_degree
= 0;
u
.clear();
}
};
class Graph
{
private:
static const int MOD
= 142857;
vector
<node
>a
;
int edge_num
, node_num
;
public:
Graph();
Graph(int node_num
);
void addEdge(int s_node
, int t_node
);
void addNodeVal(int node_index
, int val
);
int getAns();
};
Graph
::Graph() {
this->a
.clear();
this->edge_num
= this->node_num
= 0;
}
Graph
::Graph(int node_num
) {
a
.clear();
a
.resize(node_num
+5);
this->node_num
= node_num
;
this->edge_num
= 0;
}
void Graph
::addEdge(int s_node
, int t_node
) {
this->a
[s_node
].u
.push_back(t_node
);
this->a
[t_node
].in_degree
++;
this->edge_num
++;
}
void Graph
::addNodeVal(int node_index
, int val
) {
this->a
[node_index
].val
= (this->a
[node_index
].val
+ val
) % MOD
;
}
int Graph
::getAns() {
int ret
= 0;
queue
<int>q
;
for (int i
= 1; i
<= node_num
; i
++) {
if (a
[i
].in_degree
== 0) {
q
.push(i
);
}
}
while (!q
.empty()) {
node
& now
= a
[q
.front()];
q
.pop();
ret
= (ret
+ now
.val
) % MOD
;
for (int i
= 0; i
< now
.u
.size(); i
++) {
a
[now
.u
[i
]].in_degree
--;
a
[now
.u
[i
]].val
= (a
[now
.u
[i
]].val
+ now
.val
) % MOD
;
if (a
[now
.u
[i
]].in_degree
== 0) {
q
.push(now
.u
[i
]);
}
}
}
return ret
;
}
int main()
{
int n
, m
, k
;
while (cin
>> n
>> m
>> k
) {
Graph g
= Graph(n
);
while (k
--) {
int x
;
cin
>> x
;
g
.addNodeVal(x
, 1);
}
while (m
--) {
int node_s
, node_t
;
cin
>> node_s
>> node_t
;
g
.addEdge(node_s
, node_t
);
}
cout
<< g
.getAns() << endl
;
}
}
