Update use of 3 arrays in prims, add strivers video link

graph/prims.cpp

@@ -1,14 +1,19 @@
 #include <bits/stdc++.h>
 using namespace std;
 /*
+    youtube :- https://www.youtube.com/watch?v=HnD676J56ak
     LOGIC
     1.) Maintain two sets
         i.)  First set contains vertices already included in MST
         ii.) Second set contains vertices not yet included.
     
     2.) At every step consider all edges that connects two sets
         pick the minm weight edge from these edges.
-
+-----------------------------------------------------------------------------------------------------------------
+    Use 3 arrays - keys,mstSet,parent
+        keys -> it contains current vertex se connected vertices ke edge ka weight (Initialized to INT_MAX)
+        mstSet ->  boolean array used to maintain record of vertex included in min span tree
+        parent -> parent of vertices (It can be used to print min span tree at last)
 
 */
 int main()
@@ -62,4 +67,4 @@ int main()
         cout << parent[i] << " " << i << "\n";
     }
     return 0;
-}
+}