Added 3 solutions

Author: varunu28

Heaps And Maps/Magician And Chocolates.java

@@ -0,0 +1,27 @@
+public class Solution {
+    public static int nchoc(int A, ArrayList<Integer> B) {
+        final int MOD = 1000000007;
+        PriorityQueue<Integer> pq = new PriorityQueue<>(new Comparator<Integer>() {
+            @Override
+            public int compare(Integer o1, Integer o2) {
+                return o2 - o1;
+            }
+        });
+
+        for (Integer choc : B) {
+            pq.add(choc);
+        }
+
+        long total = 0;
+
+        while (A-- > 0) {
+            int choc = pq.poll();
+            total += choc;
+            total %= MOD;
+            pq.add(choc/2);
+        }
+
+        return (int) total;
+    }
+}
+

Heaps And Maps/N Max Pair Combinations.java

@@ -0,0 +1,57 @@
+import java.util.*;
+
+public class Solution {
+    public ArrayList<Integer> solve(ArrayList<Integer> A, ArrayList<Integer> B) {
+
+        int n = A.size();
+        PriorityQueue<SumElement> pq = new PriorityQueue<>(new Comparator<SumElement>() {
+            @Override
+            public int compare(SumElement o1, SumElement o2) {
+                return o2.sum - o1.sum;
+            }
+        });
+
+        Collections.sort(A);
+        Collections.sort(B);
+
+        pq.add(new SumElement(A.get(n-1) + B.get(n-1), n-1, n-1));
+
+        ArrayList<Integer> ans = new ArrayList<>();
+        Set<String> set = new HashSet<>();
+        set.add(new StringBuilder().append(n-1).append("|").append(n-1).toString());
+
+        while (n-- > 0) {
+            SumElement element = pq.poll();
+            ans.add(element.sum);
+            if (!set.contains(new StringBuilder().append(element.ind1-1).append("|").append(element.ind2).toString())) {
+                if (element.ind1-1 >= 0) {
+                    pq.add(new SumElement(A.get(element.ind1 - 1) + B.get(element.ind2), element.ind1 - 1, element.ind2));
+                    set.add(new StringBuilder().append(element.ind1-1).append("|").append(element.ind2).toString());
+                }
+            }
+
+            if (!set.contains(new StringBuilder(element.ind1).append("|").append(element.ind2-1).toString())) {
+                if (element.ind2-1 >= 0) {
+                    pq.add(new SumElement(A.get(element.ind1) + B.get(element.ind2 - 1), element.ind1, element.ind2 - 1));
+                    set.add(new StringBuilder(element.ind1).append("|").append(element.ind2-1).toString());
+                }
+            }
+        }
+
+        return ans;
+    }
+}
+
+class SumElement {
+    int sum;
+    int ind1;
+    int ind2;
+
+    public SumElement(int sum, int ind1, int ind2) {
+        this.sum = sum;
+        this.ind1 = ind1;
+        this.ind2 = ind2;
+    }
+}
+
+

Trees/Populate Next Right Pointers Tree.java

@@ -0,0 +1,40 @@
+/**
+ * Definition for binary tree with next pointer.
+ * public class TreeLinkNode {
+ *     int val;
+ *     TreeLinkNode left, right, next;
+ *     TreeLinkNode(int x) { val = x; }
+ * }
+ */
+public class Solution {
+    public void connect(TreeLinkNode root) {
+        if (root == null) {
+            return;
+        }
+        
+        Queue<TreeLinkNode> queue = new LinkedList<>();
+        queue.add(root);
+        queue.add(null);
+        
+        while (queue.peek() != null) {
+            int size = queue.size()-1;
+            
+            while (size-- > 0) {
+                TreeLinkNode node = queue.remove();
+                node.next = queue.peek();
+                
+                if (node.left != null) {
+                    queue.add(node.left);
+                }
+                
+                if (node.right != null) {
+                    queue.add(node.right);
+                }
+            }
+        
+            queue.remove();
+            queue.add(null);
+        }
+    }
+}
+