#pragma GCC diagnostic error "-std=c++11"
#pragma GCC target("avx")
#pragma GCC optimize(3)
#pragma GCC optimize("Ofast")
#pragma GCC optimize("inline")
#pragma GCC optimize("-fgcse")
#pragma GCC optimize("-fgcse-lm")
#pragma GCC optimize("-fipa-sra")
#pragma GCC optimize("-ftree-pre")
#pragma GCC optimize("-ftree-vrp")
#pragma GCC optimize("-fpeephole2")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-fsched-spec")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("-falign-jumps")
#pragma GCC optimize("-falign-loops")
#pragma GCC optimize("-falign-labels")
#pragma GCC optimize("-fdevirtualize")
#pragma GCC optimize("-fcaller-saves")
#pragma GCC optimize("-fcrossjumping")
#pragma GCC optimize("-fthread-jumps")
#pragma GCC optimize("-funroll-loops")
#pragma GCC optimize("-fwhole-program")
#pragma GCC optimize("-freorder-blocks")
#pragma GCC optimize("-fschedule-insns")
#pragma GCC optimize("inline-functions")
#pragma GCC optimize("-ftree-tail-merge")
#pragma GCC optimize("-fschedule-insns2")
#pragma GCC optimize("-fstrict-aliasing")
#pragma GCC optimize("-fstrict-overflow")
#pragma GCC optimize("-falign-functions")
#pragma GCC optimize("-fcse-skip-blocks")
#pragma GCC optimize("-fcse-follow-jumps")
#pragma GCC optimize("-fsched-interblock")
#pragma GCC optimize("-fpartial-inlining")
#pragma GCC optimize("no-stack-protector")
#pragma GCC optimize("-freorder-functions")
#pragma GCC optimize("-findirect-inlining")
#pragma GCC optimize("-fhoist-adjacent-loads")
#pragma GCC optimize("-frerun-cse-after-loop")
#pragma GCC optimize("inline-small-functions")
#pragma GCC optimize("-finline-small-functions")
#pragma GCC optimize("-ftree-switch-conversion")
#pragma GCC optimize("-foptimize-sibling-calls")
#pragma GCC optimize("-fexpensive-optimizations")
#pragma GCC optimize("-funsafe-loop-optimizations")
#pragma GCC optimize("inline-functions-called-once")
#pragma GCC optimize("-fdelete-null-pointer-checks")
#pragma GCC optimize("Ofast,fast-math,unroll-loops")
试试这些加速头文件
by 灿若琉璃 @ 2019-01-30 10:00:21
过了，原来是该死用了stl的stack
```cpp
#include<cstdio>
#include<algorithm>
#include<cstring>
//#include<stack>
using namespace std;
const int MAXN=10010,MAXM=50010;
int n,m,ans=0;
int first[MAXN];
struct edge{
int u,v,next;
}e[MAXM];
int tot=0;
void insert(int u,int v){
tot++;e[tot].u=u;e[tot].v=v;e[tot].next=first[u];first[u]=tot;
}
//stack<int> s;
int stack[MAXN],top=0;
int deepdark=0;
int dfn[MAXN]={0},low[MAXN]={0},ins[MAXN]={0};
void tarjan(int u){
dfn[u]=low[u]=++deepdark;
ins[u]=1;
//s.push(u);
top++;stack[top]=u;
for(int i=first[u];i!=-1;i=e[i].next){
int v=e[i].v;
if(dfn[v]==0){
tarjan(v);
low[u]=min(low[u],low[v]);
}
else if(ins[v]){
low[u]=min(low[u],dfn[v]);
}
}
if(dfn[u]==low[u]){
int qwq=0;
while(s.top()!=u){
ins[/*s.top()*/stack[top]]=0;
//s.pop();
top--;
qwq++;
}
ins[u]=0;//s.pop();
top--;
qwq++;
if(qwq>1)ans++;
}
}
int main(){
memset(first,-1,sizeof(first));
scanf("%d%d",&n,&m);
int x,y;
for(int i=1;i<=m;i++){
scanf("%d%d",&x,&y);
insert(x,y);
}
for(int i=1;i<=n;i++){
if(dfn[i]==0){
tarjan(i);
}
}
printf("%d",ans);
return 0;
}
```
by Dark_Van @ 2019-01-30 10:11:30