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Copy pathalgorithm.kosaraju.cpp
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127 lines (79 loc) · 2.07 KB
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#include <cstdio>
#include <vector>
#include <stack>
#include <cstring>
#define MAXN 100001
#define FIN "ctc.in"
#define FOUT "ctc.out"
using namespace std;
vector<int> Graph[ MAXN ];
vector<int> Graph_REVERSE[ MAXN ];
stack<int> Stack;
bool isVisited[ MAXN ];
vector<int> Results[ MAXN ];
int nodes,//number of nodes
edges, //number of edges
comp;//this holds the components strongly connex;
void readData() {
int x,
y;
freopen(FIN, "r", stdin);
scanf("%d %d", &nodes, &edges);
for(int i = 1; i <= edges; i++) {
scanf("%d %d", &x, &y);
Graph[ x ].push_back( y );
Graph_REVERSE[ y ].push_back( x );
}
fclose( stdin );
};
void DFS(int node) {
isVisited[ node ] = 1;
for(vector<int>::iterator it = Graph[ node ].begin(); it != Graph[ node ].end(); ++it) {
if(!isVisited[ *it ]) {
DFS( *it );
}
}
Stack.push( node );
};
void DFS_REVERSE(int node) {
isVisited[ node ] = 1;
Results[ comp ].push_back( node );
for(vector<int>::iterator it = Graph_REVERSE[ node ].begin(); it != Graph_REVERSE[ node ].end(); ++it) {
if(!isVisited[ *it ]) {
DFS_REVERSE( *it );
}
}
};
void Kosaraju() {
int vertex = 0;
for(int i = 1; i <= nodes; i++)
if( !isVisited[ i ] ) {
DFS( i );
}
memset(isVisited, 0, sizeof(isVisited));
while( !Stack.empty() ){
vertex = Stack.top();
Stack.pop();
if(!isVisited[ vertex ]) {
comp++;
DFS_REVERSE( vertex );
}
}
};
void writeData() {
freopen(FOUT, "w", stdout);
printf("%d\n", comp);
for(int i = 1; i <= comp; i++) {
for(vector<int>::iterator it = Results[ i ].begin(); it != Results[ i ].end(); ++it) {
printf("%d ", *it);
}
printf("\n");
}
fclose( stdout );
};
int main() {
readData();
Kosaraju();
writeData();
return(0);
};