F - Perils in Parallel

类似于差分异或前缀和， 将区间操作连成图， 跑一便

#include <bits/stdc++.h>
using namespace std ;
const int N = 2e5 + 10 ;
int a[N] , b[N] , c[N] , d[N] ;
int n , m ;
int h[N * 2] , ne[N * 2] , e[N * 2] , w[N * 2] , vis[N * 2] ;
int idx , use[N] ;
int get(int x)
{
  return lower_bound(d + 1 , d + n + 1 , x) - d ;
}
void add(int a , int b , int c)
{
  e[idx] = b , ne[idx] = h[a] , w[idx] = c ,  h[a] = idx ++ ;
}
int dfs(int u)
{
  vis[u] = 1 ;
  int x = c[u] ;
  for(int i = h[u] ; ~i ; i = ne[i])
   {
     int v = e[i] ;
     if(!vis[v] && dfs(v))
      x ^= 1 , use[w[i]] = 1 ;
   }
  return x ;
}
int main()
{
  for(int i = 0 ;i < N ;i ++) h[i] = -1 ;
  ios::sync_with_stdio(false) ;
  cin.tie(0) , cout.tie(0) ;
  cin >> n >> m ;
  for(int i = 1; i <= n ; i ++) cin >> a[i] >> b[i] , d[i] = a[i] ;
  sort(d + 1 , d + n + 1) ;
  for(int i = 1; i <= n ;i ++)
   c[get(a[i])] = b[i] ;
  for(int i = n + 1; i >= 1 ;i --) c[i] ^= c[i - 1] ;
  for(int i = 1; i <= m ;i ++)
   {
     int l , r ;
     cin >> l >> r ;
     l = get(l) , r = lower_bound(d + 1 , d + n + 1 , r + 1 ) - d  ;

  // cout << r << " rr " ;

     if(l <= r)
     add(l , r  , i) , add(r  , l , i) ;
   }
   // puts("") ;
   for(int i = 1; i <= n + 1 ;i ++)
    if(!vis[i] && dfs(i))
     {
       cout << -1 << endl ;
       return 0 ;
     }
     int ans =  0 ;
     for(int i = 1; i <= m ;i ++)
      if(use[i]) ans ++ ;
    cout << ans << endl ;
    for(int i = 1;i <= m ;i ++)
     if(use[i])
      cout << i << " " ;
}