用數組模擬雙鏈表

#include<iostream>
using namespace std;
const int N = 100010;
int l[N],r[N],e[N],idx;
void add(int k,int x){
    e[idx] = x;
    l[idx] = k;
    r[idx] = r[k];
    l[r[k]] = idx;
    r[k] = idx;
    idx++;
}
void del(int k){
   r[l[k]] = r[k];
   l[r[k]] = l[k];
}
void init(){
    r[0] = 1;
    l[1] = 0;
    idx =2;
}