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--- study_2 [2020/06/15 00:15] – created jrseti
+++ study_2 [2020/11/03 21:32] (current) – jrseti
@@ Line 1: / Line 1: @@
-==Binary Heaps==
+=====One hour interview Video====
+https://www.youtube.com/watch?v=3yQ4Jaumw3g
+====Binary Heaps====
 [[https://bradfieldcs.com/algos/trees/priority-queues-with-binary-heaps/|Good Binary Heap Tutorial]]
 enqueue or dequeue items in O(logn)
+**Priority Queues** use a min heap or max heap. In Java use the Comparator:
+<code>
+import java.util.*;
+...
+PriorityQueue<Student> pq = new PriorityQueue<Student>(5, new StudentComparator());
+...
+Class StudentComparator implements Comparator<Student>{
+            // Overriding compare()method of Comparator
+                        // for descending order of cgpa
+            public int compare(Student s1, Student s2) {
+                if (s1.cgpa < s2.cgpa)
+                    return 1;
+                else if (s1.cgpa > s2.cgpa)
+                    return -1;
+                                return 0;
+                }
+        }
+</code>
+====Reverse Singly Linked List====
+  prev = None
+  cur = head
+  while cur:
+    next_node = cur.next
+    cur.next = prev
+    prev = cur
+    cur = next_node
+  head = prev
+====Reverse Double Linked List====
+<code>
+void reverse() {
+        Node temp = null;
+        Node current = head;
+        /* swap next and prev for all nodes of
+         doubly linked list */
+        while (current != null) {
+            temp = current.prev;
+            current.prev = current.next;
+            current.next = temp;
+            current = current.prev;
+        }
+        /* Before changing head, check for the cases like empty
+         list and list with only one node */
+        if (temp != null) {
+            head = temp.prev;
+        }
+    }
+</code>
+====Power Sets====
+All combinations of letters in a string.
+Trick = use an integer counter.
+<code>
+        /*set_size of power set of a set
+        with set_size n is (2**n -1)*/
+        long pow_set_size =
+            (long)Math.pow(2, set_size);
+        int counter, j;
+        /*Run from counter 000..0 to
+..1*/
+        for(counter = 0; counter <
+                pow_set_size; counter++)
+        {
+            for(j = 0; j < set_size; j++)
+            {
+                /* Check if jth bit in the
+                counter is set If set then
+                print jth element from set */
+                if((counter & (1 << j)) > 0)
+                    System.out.print(set[j]);
+            }
+            System.out.println();
+        }
+</code>
+====Tries====
+====N Choose K====
+n!/((n-k)!k!)
+====Knapsack====
+====Coins====
+====Quick Sort====
+====Heaps====
+====Spiral====
+====Quick Sort====
+====Priority Queues====