55 lines
858 B
C++
55 lines
858 B
C++
#include <bits/stdc++.h>
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using namespace std;
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vector<bool> visitedNodes;
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vector<vector<int>> edgeList;
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void dfs(int start){
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visitedNodes[start] = true;
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for(int node : edgeList[start]){
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if(!visitedNodes[node]){
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dfs(node);
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}
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}
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}
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int main(){
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ios::sync_with_stdio(0);
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cin.tie(0);
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int n, m;
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cin >> n >> m;
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if(n != m){
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cout << 0 << endl;
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return 0;
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}
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visitedNodes.reserve(n+1);
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edgeList.reserve(n+1);
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for(int i = 1; i <= m; ++i){
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int u, v;
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cin >> u >> v;
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edgeList[u].push_back(v);
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}
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long long result = 1;
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for(int start = 1; start <= n; ++start){
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if(!visitedNodes[start]){
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result = (result * 2) % 998244353;
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dfs(start);
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}
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}
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cout << result;
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cout << flush;
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return 0;
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} |