https://codeforc.es/contest/1214/problem/E
借鉴自dls的做法：先把奇数号从长到短连接起来然后连剩下的偶数号。
1 #define bug(x) cout<<#x<<" is "<<x<<endl 2 #define IO std::ios::sync_with_stdio(0) 3 #include <bits/stdc++.h> 4 #define iter ::iterator 5 #define pa pair<int,int> 6 using namespace std; 7 #define ll long long 8 #define mk make_pair 9 #define pb push_back 10 #define se second 11 #define fi first 12 #define ls o<<1 13 #define rs o<<1|1 14 ll mod=998244353; 15 const int N=2e5+5; 16 int n; 17 pa p[N]; 18 vector<pa>ans; 19 int pos[N]; 20 int main(){ 21 IO; 22 cin>>n; 23 for(int i=1;i<=n;i++){ 24 cin>>p[i].fi; 25 p[i].se=i; 26 } 27 sort(p+1,p+1+n); 28 reverse(p+1,p+1+n); 29 for(int i=1;i<=n;i++){ 30 pos[i]=p[i].se*2-1; 31 if(i>1){ 32 ans.pb(mk(pos[i-1],pos[i])); 33 } 34 } 35 int len=n; 36 for(int i=1;i<=n;i++){ 37 int c=i+p[i].fi; 38 if(c==len+1){ 39 pos[c]=p[i].se*2; 40 ans.pb(mk(pos[c-1],pos[c])); 41 len++; 42 } 43 else{ 44 ans.pb(mk(pos[c-1],2*p[i].se)); 45 } 46 } 47 for(auto p: ans){ 48 cout<<p.fi<<" "<<p.se<<endl; 49 } 50 }