ACM常用模板 有向图强连通分支(dfs邻接阵形

//有向图强连通分支,dfs邻接阵形式,O(n^2)
//返回分支数,id返回1..分支数的值
//传入图的大小n和邻接阵mat,不相邻点边权0
#define MAXN 100

void search(int n,int mat[][MAXN],int* dfn,int* low,int now,int& cnt,int& tag,int* id,int* st,int& sp){
int i,j;
dfn[st[sp++]=now]=low[now]=++cnt;
for (i=0;iif (mat[now][i]){
if (!dfn[i]){
ssearch(n,mat,dfn,low,i,cnt,tag,id,st,sp);
if (low[i]low[now]=low[i];
}
else if (dfn[i]for (j=0;jif (jlow[now]=dfn[i];
}
}
if (low[now]==dfn[now])
for (tag++;st[sp]!=now;id[st[--sp]]=tag);
}

int find_components(int n,int mat[][MAXN],int* id){
int ret=0,i,cnt,sp,st[MAXN],dfn[MAXN],low[MAXN];
for (i=0;ifor (sp=cnt=i=0;iif (!dfn[i])
search(n,mat,dfn,low,i,cnt,ret,id,st,sp);
return ret;
}