【DayDayUp】【算法_图_强连通_之一_Kosaraju算法和Tarjan算法】

#include <cstdio>
#include <iostream>
#include <cstring>
#include <queue>
#include <algorithm>
#include <cmath>
#include <vector>
using namespace std;
int n, m, ans;
#define N 10100
std::vector<int> v
;
int vis
, dfn
, low
, stk
, top, ins
, clk;
void Tarjon(int x){
dfn[x] = low[x] = clk++;
stk[top++] = x;
vis[x] = ins[x] = 1;
for(int j = 0;j < v[x].size();j++){
int y = v[x][j];
if(!vis[y]){
Tarjon(y);
low[x] = min(low[x], low[y]);
} else if(ins[y]){
low[x] = min(low[x], dfn[y]);
}
}
if(low[x] == dfn[x]){
int sz = 0;
do {
ins[stk[top-1]] = 0;
low[stk[top-1]] = low[x];
top--;
sz++;
} while(stk[top] != x);
if(sz > 1) ans++;
}
}
int main()
{
while(~scanf("%d%d", &n, &m)){
memset(v, 0, sizeof(v));
for(int i = 0;i < m;i++){
int x, y;scanf("%d%d", &x, &y);
x--; y--;
v[x].push_back(y);
}
memset(vis, 0, sizeof(vis));
memset(ins, 0, sizeof(ins));
top = ans = clk = 0;
clk = 1;
for(int i = 0;i < n;i++) if(!vis[i])
Tarjon(i);

for(int i = 0;i<n;i++){
cout<<i<<" "<<dfn[i]<<" "<<low[i]<<endl;
}
printf("%d\n", ans);
}
return 0;
}

/*
7 8
1 2
2 3
3 4
4 5
5 6
6 2
5 7
7 1

*/