Data structures 1

lists1p.cpp

const int N = 100000;
const int K = 1000;

int cnt = 0;
int elems[N];
int nxt[N];

int lists[K];

void add(int list, int new_elem) {
  elems[cnt] = new_elem;
  nxt[cnt] = -1;
  
  int list_p = lists[list];
  if (list_p = -1) {
    lists[list] = cnt;
    cnt++
  } else {
    while (nxt[list_p] != -1) {
      list_p = nxt[list_p];
    }

    nxt[list_p] = cnt;
    cnt++;
  }
}

void remove(int list, int idx) {
  if (idx == 0) {
    lists[list] = nxt[lists[list]];
    return;
  } else {
    int list_p = lists[list];
    while (nxt[list_p] != -1 && idx > 1) {
      list_p = nxt[list_p];
      idx--;
    }
    
    if (idx == 1 && nxt[list_p] != -1) {
      nxt[list_p] = nxt[nxt[list_p]];
    }
  }
}

int join(int list1, int list2) {
  ???
}

lists2p.cpp

const int N = 100000;
const int K = 1000;

int cnt = 0;
int elems[N];
int nxt[N];
int prev[N];

int lists[K];

void add(int list, int new_elem) {
  elems[cnt] = new_elem;
  nxt[cnt] = -1;
  
  int list_p = lists[list];
  if (list_p = -1) {
    lists[list] = cnt;
    prev[cnt] = -1;
    cnt++
  } else {
    while (nxt[list_p] != -1) {
      list_p = nxt[list_p];
    }

    nxt[list_p] = cnt;
    prev[cnt] = list_p;
    cnt++;
  }
}

void remove(int list, int idx) {
  ???
}