Initializing an Array C++ - c++

Question

My code is trying to implement the union-find algorithm and I have the id[] array and the sz[] array. I initialize them in the Union-Find constructor, but once I try to use those arrays in the methods within the Union-Find class, it changes all the array values to 1. I don't understand why. Is there something obvious that I'm missing??
H File
class UnionFind{
public:
UnionFind(int size);
void join(int x, int y);
int connected(int x, int y);
int find(int x);
private:
int size;
int id[];
int sz[];
};
CPP File
UnionFind::UnionFind(int size){
this->id[size] = id[size];
for(int i = 0; i < size; i++){
id[i] = i;
}
for(int i = 0; i < size; i++){
sz[i] = 1;
}
}
int UnionFind::find(int l){
//Path Compression Finding the Root
for(int i = 0; i < 5; i++){
}
while(l != id[l]){
id[l] = id[id[l]];
l = id[l];
}
return l;
}
void UnionFind::join(int x, int y){
int m = find(x);
int n = find(y);
if(sz[m] < sz[n]){
id[m] = n;
sz[n] += sz[m];
}
else{
id[n] = m;
sz[m] += sz[n];
}
}
int UnionFind::connected(int x, int y){
if(find(x) == find(y)){
return 1;
}
else{
return 0;
}
}

Answer 1

From the comments.
you can't have int id[] as a class member,
use std::vector (resize and fill in constructor),
your forgot to set member size in constructor,
your find algorithm uses path halving not path compression (this does not affect the running time).
Side note: you can use a single array/vector to implement your disjoint set data structure.