Codeforces Round #285 (Div.1) A Misha and Forest
水题水题水……
题意：给你一些点，给出他们连通了多少个点以及这些点的下标的异或值，让你找出一个图
题解：拓扑排序一发
代码:
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <vector>
#include <queue>
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
const int maxn = pow(2,16)+10;
vector<pair<ll,ll> >ans;
queue<ll> q;
int d[maxn],v[maxn];
bool u[maxn];
int n;
int main()
{
#ifndef ONLINE_JUDGE
//freopen("F.in","r",stdin);
//freopen("F.out","w",stdout);
#endif
cin >> n;
for(ll i =0;i<n;i++)
{
cin >> d[i]>>v[i];
if(d[i]<2)
{
q.push(i);
u[i]=1;
}
}
int t,tt,ttt;
while(!q.empty())
{
t = q.front();
q.pop();
if(d[t]==0)
continue;
tt=v[t];
v[tt] ^=t;
d[t]--;
d[tt]--;
ans.push_back(make_pair(t,tt));
if(d[tt]<2 && !u[tt])
{
q.push(tt);
u[tt]=1;
}
}
cout << ans.size() << endl;
for(auto a:ans)
{
cout << a.first <<" " << a.second << endl;
}
return 0;
}