HDU1814Peaceful Commission求2-sa最小字典序

#include <iostream>
#include <cstdio>
#include <vector>
#include <cstring>
#include <queue>
using namespace std;
const int maxn = 16100;
struct node {
     int v,next;
} edge[41000];
int head[maxn],sta[maxn],vis[maxn];
int id,top,n;
void add_edge(int u,int v){
     edge[id].v = v;edge[id].next = head[u];head[u] = id++;
}
int dfs(int u){
    if( vis[u^1] )return 0;
    if( vis[u])return 1;

    vis[u] = 1;
    sta[top++] = u;
    for(int id = head[u]; id != -1; id = edge[id].next)
    if(!dfs(edge[id].v))return 0;
    return 1;
}
int slove(){
    memset(vis,0,sizeof(vis));

    for(int v = 0; v < n*2; v += 2){
        if( vis[v] || vis[v^1])continue;
        top = 0;
        if(!dfs(v)){
            while(top)vis[sta[--top]] = 0;
            if( !dfs(v^1))return 0;
        }
    }
    return 1;
}
int main()
{
     int m;
     int u,v;
     while(~scanf("%d%d",&n,&m)) {
          memset(head,-1,sizeof(head));
          id = 0;
          for(int i = 0; i < m; i ++) {
               scanf("%d%d",&u,&v);
            u--;v--;
            add_edge(u,v^1);
            add_edge(v,u^1);
          }
          if( !slove())puts("NIE");
          else {
                for(int i = 0; i < n*2; i+= 2){
                    printf("%d\n",(vis[i]?i:i^1) + 1);
                }
          }
     }
     return 0;
}