学渣乱搞系列之Tarjan模板合集

学渣乱搞系列之Tarjan模板合集

　　　　　　　　　　　　by　狂徒归来

一、求强连通子图

 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <cmath>
 #include <algorithm>
 #include <climits>
 #include <vector>
 #include <queue>
 #include <cstdlib>
 #include <string>
 #include <set>
 #include <stack>
 #define LL long long
 #define pii pair<int,int>
 #define INF 0x3f3f3f3f
 using namespace std;
 const int maxn = ;
 int dfn[maxn],low[maxn],belong[maxn];
 bool instack[maxn];
 vector<int>g[maxn];
 stack<int>stk;
 int n,m,cnt,scc;
 void tarjan(int u) {
     dfn[u] = low[u] = ++cnt;
     stk.push(u);
     instack[u] = true;
     for(int i = ; i < g[u].size(); i++) {
         if(!dfn[g[u][i]]) {
             tarjan(g[u][i]);
             low[u] = min(low[u],low[g[u][i]]);
         } else if(instack[g[u][i]]) low[u] = min(low[u],dfn[g[u][i]]);
     }
     if(dfn[u] == low[u]) {
         scc++;
         int v;
         do {
             v = stk.top();
             instack[v] = false;
             belong[v] = scc;
             stk.pop();
         } while(v != u);//每一个强连通块内de点，以及其属于的scc
     }
 }
 int main() {
     int i,j,u,v,a,b;
     while(~scanf("%d %d",&n,&m)) {
         for(i = ; i <= n; i++) {
             dfn[i] = belong[i] = ;
             instack[i] = false;
             g[i].clear();
         }
         cnt = scc = ;
         while(!stk.empty()) stk.pop();
         for(i = ; i <= m; i++) {
             scanf("%d %d",&u,&v);
             g[u].push_back(v);
         }
         for(i = ; i <= n; i++)
             if(!dfn[i]) tarjan(i);
     }
     return ;
 }

二、求割点

 const int maxn = ;
 vector<int>g[maxn];
 bool iscut[maxn];
 int dfn[maxn],low[maxn],cnt,vis[maxn];
 void tarjan(int u,int fa) {
     dfn[u] = low[u] = ++cnt;
     vis[u] = ;
     int son = ;
     for(int i = ; i < g[u].size(); i++) {
         if(!vis[g[u][i]]) {
             tarjan(g[u][i],u);
             son++;
             low[u] = min(low[u],low[g[u][i]]);
             if(fa == - && son >  || fa != - && low[g[u][i]] >= dfn[u])
                 iscut[u] = true;
         } else if(vis[g[u][i]] == ) low[u] = min(low[u],dfn[g[u][i]]);
     }
     vis[u] = ;
 }

三、求割边/桥

 int ret;
 void tarjan(int u,int fa) {
     dfn[u] = low[u] = ++clk;
     bool flag = false;
     for(int i = head[u]; ~i; i = e[i].next) {
         if(!flag && e[i].to == fa) {
             flag = true;
             continue;
         }
         if(!dfn[e[i].to]) {
             tarjan(e[i].to,u);
             low[u] = min(low[u],low[e[i].to]);
             if(low[e[i].to] > dfn[u]) {
                 e[i].cut = e[i^].cut = true;
                 ++ret;
             }
         } else low[u] = min(low[u],dfn[e[i].to]);
     }
 }

四、求LCA