Created
October 27, 2014 18:41
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| #include <iostream> | |
| #include <iterator> | |
| #include <set> | |
| #include <vector> | |
| #include <algorithm> | |
| #include <cassert> | |
| #include <cmath> | |
| using namespace std; | |
| typedef unsigned long long input_type; | |
| typedef vector<vector<input_type> > InputContainer; | |
| void prepare_graph(InputContainer& container, input_type n) | |
| { | |
| container.resize(n); | |
| } | |
| void add_edge(InputContainer& container, input_type from_point, input_type to_point) | |
| { | |
| container[from_point - 1].push_back(to_point - 1); | |
| } | |
| void explore_path(const InputContainer& container, const input_type index, vector<bool>& v, vector<input_type>& path) | |
| { | |
| v[index] = true; | |
| const vector<input_type>& a = container[index]; | |
| for (input_type i = 0; i < a.size(); ++i) { | |
| const input_type& next_index = a[i]; | |
| if (!v[next_index]) { | |
| explore_path(container, next_index, v, path); | |
| } | |
| } | |
| path.push_back(index); | |
| } | |
| void explore(const InputContainer& container, vector<input_type>& whole_path) | |
| { | |
| vector<bool> v(container.size(), false); | |
| for (input_type i = 0; i < v.size(); ++i) { | |
| if (!v[i]) { | |
| explore_path(container, i, v, whole_path); | |
| } | |
| } | |
| } | |
| int main() | |
| { | |
| input_type n = 0, m = 0; | |
| cin >> n >> m; | |
| InputContainer input, inversed_input; | |
| prepare_graph(input, n); | |
| prepare_graph(inversed_input, n); | |
| for (input_type i = 0; i < m; ++i) { | |
| input_type first, second; | |
| cin >> first >> second; | |
| add_edge(input, first, second); | |
| add_edge(inversed_input, second, first); | |
| } | |
| vector<input_type> path; | |
| explore(inversed_input, path); | |
| assert(path.size() == n); | |
| vector<bool> v(input.size(), false); | |
| input_type count = 0; | |
| while (path.size()) { | |
| input_type i = path.back(); | |
| path.pop_back(); | |
| vector<input_type> p; | |
| if (!v[i]) { | |
| explore_path(input, i, v, p); | |
| assert(p.size() != 0); | |
| ++count; | |
| } | |
| } | |
| cout << count; | |
| return 0; | |
| } |
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Sample Input:
4 4
1 2
4 1
2 3
3 1
Sample Output:
2