Merge pull request #1 from AayushVyasKIIT/AayushVyasKIIT-DSU-CLASS-BASED

Class based DSU : Path Compression O(1) & Union Rank O(logN)

data_structures/DSU_path_compresssion.cpp

@@ -4,13 +4,20 @@ using namespace std;
 
 #define vi vector<int>
 
+//Disjoint set union 
 class DSU{
     private:
+        // p: keeps track of parent of i
+        // depth: tracks the depth of i
+        // setSize: size of each chunk(set)
+        // maxElement : max of each set, using maxElement[representative]
+        // minElement : min of each set, using minElement[representative]
         vi p,depth,setSize,maxElement,minElement;
     public:
+        // parameter : int n -> maximum number of items
         DSU(int n){
             p.assign(n,0);
-            //initially all of them are their parents.
+            //initially all of them are their own parents.
             for(int i=0;i<n;i++){
                 p[i] = i;
             }
@@ -35,11 +42,12 @@ class DSU{
             if(p[i]==i){
                 return i;
             }
-            //path compression
+            //path compression i -> root(representative)
             return (p[i] = findSet(p[i]));
         }
         //union of 2 sets
         void UnionSet(int i,int j){
+            //check if both belongs to same set or not
             if(isSame(i,j)){
                 return;
             }
@@ -56,22 +64,24 @@ class DSU{
             //making the shallower root's parent the deeper root
             p[x] = y;
             
+            //if same depth then increase one's depth
             if(depth[x] == depth[y]){
                 depth[y]++;
             }
             //total size of the resultant set.  
             setSize[y] += setSize[x];
+            //changing the maximum elements
             maxElement[y] = max(maxElement[x],maxElement[y]);
             minElement[y] = min(minElement[x],minElement[y]);
         }
-        //checks if both sets equal
-
+        //checks if both belongs to same set
         bool isSame(int i,int j){
             if(findSet(i) == findSet(j)){
                 return true;
             }
             return false;
         }
+        //returns min max size of i's set
         void get(int i){
             cout << get_min(i) << " " << get_max(i) << " " <<size(i) << endl; 
         }
@@ -79,19 +89,45 @@ class DSU{
         int size(int i){
             return setSize[findSet(i)];
         }
+        //returns max of the set whose part is i
         int get_max(int i){
             return maxElement[findSet(i)];
         }
+        //returns min of the set whose part is i
         int get_min(int i){
             return minElement[findSet(i)];
         }
 
 };
-
+/*
+test case#1:
+        5 11
+        union 1 2
+        get 3
+        get 2
+        union 2 3
+        get 2
+        union 1 3
+        get 5
+        union 4 5
+        get 5
+        union 4 1
+        get 5
+*/
+/*
+output case#1:
+        3 3 1
+        1 2 2
+        1 3 3
+        5 5 1
+        4 5 2
+        1 5 5
+*/
 int main(){
     std::ios_base::sync_with_stdio(0);std::cin.tie(0);std::cout.tie(0);
     int n,q;cin>>n;cin>>q;
-
+    //n: number of items
+    //q: number of queries to be made
     DSU d(n+1);
 
     while(q--){
@@ -99,11 +135,11 @@ int main(){
         if(op == "union"){
             int i,j;
             cin >> i >> j;
-            d.UnionSet(i,j);
+            d.UnionSet(i,j); //performs union operation on i and j
         }else{
             int i;
             cin >> i;
-            d.get(i);
+            d.get(i); //print min max and size of set.
         }
     }
     

data_structures/DSU_union_rank.cpp

@@ -5,10 +5,15 @@ using namespace std;
 #define vi vector<int> 
 class DSU{
     private:
+        // p: keeps track of parent of i
+        // depth: tracks the depth of i
+        // setSize: size of each chunk(set)
         vi p,depth,setSize;
     public:
+        //parameter : int n -> maximum number of items
         DSU(int n){
             p.assign(n,0);
+            //initially all of them their own parents
             depth.assign(n,0);
             setSize.assign(n,0);
             for(int i=0;i<n;i++){
@@ -18,27 +23,38 @@ class DSU{
             }
         }
         int findSet(int i){
+            //union rank i - > p[i]
             while(i!=p[i]){
                 i = p[i];
             }
             return i;
         }
+        //union of 2 sets
         void unionSet(int i,int j){
+            //check if both belongs to same set or not
             if(isSame(i,j)){
                 return;
             }
+            //we find representative of the i and j
             int x = findSet(i);
             int y = findSet(j);
 
+            //always keeping the min as x
+            //in order to create a shallow tree
             if(depth[x]>depth[y]){
                 swap(x,y);
             }
+            //making the shallower tree' root parent of the deeper root
             p[x] = y;
+
+            //if same depth then increase one's depth
             if(depth[x] == depth[y]){
                 depth[y]++;
             }
+            //total size of the resultant set
             setSize[y]+=setSize[x];
         }
+        // checks if both belongs to same set
         bool isSame(int i,int j){
             if(findSet(i) == findSet(j)){
                 return true;
@@ -49,9 +65,11 @@ class DSU{
 };
 
 int main(){
+    //number of items
     int n;cin>>n;
 
     DSU d(n+1);
+    //perform operations here
     d.unionSet(2,4);
     d.unionSet(3,4);
     cout <<  d.findSet(2) <<endl;