P1726 上白澤慧音 - 強連通分量模板

標籤：強連通分量   algorithm   using   stack   efi   ++   name   tar   有向圖   

雖然是模板但是卻提醒我有向圖一定要試著從每個點出發，不僅僅是因為圖不一定連通，更有可能是只從1號點出發哪也去不了的情況

#include <algorithm>#include <iostream>#include <cstring>#include <cstdio>#include <stack>using namespace std;#define debug(x) cerr << #x << "=" << x << endl;const int MAXN = 10000 + 10;stack<int> s;int n,m,vis[MAXN],last[MAXN],edge_tot,temp[MAXN],fina[MAXN],ans,dfn[MAXN],low[MAXN],flg[MAXN],cnt;struct Edge{    int u, v, w, to;    Edge(){}    Edge(int u, int v, int to) : u(u), v(v), to(to) {}}e[50001 * 2];inline void add(int u, int v) {    e[++edge_tot] = Edge(u, v, last[u]);    last[u] = edge_tot; }bool cmp(int a, int b) {    return a < b;}void tarjan(int x) {    dfn[x] = low[x] = ++cnt;    s.push(x);    flg[x] = true;    for(int i=last[x]; i; i=e[i].to) {        int v = e[i].v;        if(!dfn[v]) {            tarjan(v);            if(low[v] < low[x]) low[x] = low[v];        } else if(dfn[v] < low[x] && flg[v]) {            low[x] = dfn[v];        }    }    if(dfn[x] == low[x]) {        int j, num=0;        do{            j = s.top();            s.pop();            temp[++num] = j;             flg[j] = 0;        }while(j != x);        sort(temp+1, temp+num+1, cmp);        if(num > ans) {            memcpy(fina, temp, sizeof(temp));            ans = num;        } else if(num == ans) {            if(memcmp(fina, temp, sizeof(temp)) > 0)                 memcpy(fina, temp, sizeof(temp));        }    }    }int main() {    scanf("%d%d", &n, &m);    for(int i=1; i<=m; i++) {        int a,b,t;        scanf("%d%d%d",&a, &b, &t);        add(a, b);        if(t == 2) add (b, a);    }    for(int i=1; i<=n; i++)         if(!dfn[i]) //關鍵之處            tarjan(i);    printf("%d\n", ans);    for(int i=1; i<=ans; i++) {        printf("%d ", fina[i]);    }    return 0;} 

P1726 上白澤慧音 - 強連通分量模板