Candy

Author: gouthampradhan

README.md

@@ -210,6 +210,7 @@ My accepted leetcode solutions to some of the common interview problems.
 - [The Skyline Problem](problems/src/heap/TheSkylineProblem.java) (Hard)
 - [Meeting Rooms II](problems/src/heap/MeetingRoomsII.java) (Medium)
 - [Top K Frequent Words](problems/src/heap/TopKFrequentWords.java) (Medium)
+- [Candy](problems/src/heap/Candy.java) (Hard)
 
 #### [Linked List](problems/src/linked_list)
 

problems/src/heap/Candy.java

@@ -0,0 +1,92 @@
+package heap;
+
+import java.util.*;
+
+/**
+ * Created by gouthamvidyapradhan on 26/07/2018.
+ * There are N children standing in a line. Each child is assigned a rating value.
+
+ You are giving candies to these children subjected to the following requirements:
+
+ Each child must have at least one candy.
+ Children with a higher rating get more candies than their neighbors.
+ What is the minimum candies you must give?
+
+ Example 1:
+
+ Input: [1,0,2]
+ Output: 5
+ Explanation: You can allocate to the first, second and third child with 2, 1, 2 candies respectively.
+ Example 2:
+
+ Input: [1,2,2]
+ Output: 4
+ Explanation: You can allocate to the first, second and third child with 1, 2, 1 candies respectively.
+ The third child gets 1 candy because it satisfies the above two conditions.
+
+ Solution: O(N log N): Store the indexes in a heap, iterate through the heap one by one and assign candies one
+ greater than its neighbours. Take care of edge cases.
+
+ */
+public class Candy {
+
+    /**
+     * Main method
+     * @param args
+     * @throws Exception
+     */
+    public static void main(String[] args) throws Exception{
+        int[] ratings = {29,51,87,87,72,12};
+        System.out.println(new Candy().candy(ratings));
+    }
+
+    public int candy(int[] ratings) {
+        if(ratings.length == 1) return 1;
+        PriorityQueue<Integer> pq = new PriorityQueue<>((o1, o2) -> Integer.compare(ratings[o1], ratings[o2]));
+        for(int i = 0; i < ratings.length; i ++){
+            pq.offer(i);
+        }
+        int[] count = new int[ratings.length];
+        while (!pq.isEmpty()){
+            int index = pq.poll();
+            if(index - 1 < 0){
+                if(ratings[index + 1] == ratings[index]){
+                    count[index] = 1;
+                } else{
+                    count[index] = count[index + 1] + 1;
+                }
+            } else if(index + 1 >= ratings.length) {
+                if(ratings[index - 1] == ratings[index]){
+                    count[index] = 1;
+                } else{
+                    count[index] = count[index - 1] + 1;
+                }
+            } else{
+                if((ratings[index - 1] == ratings[index]) && (ratings[index + 1] == ratings[index])){
+                    count[index] = 1;
+                } else{
+                    if(((ratings[index - 1] == ratings[index]) && (ratings[index + 1] > ratings[index]))
+                            || ((ratings[index + 1] == ratings[index]) && (ratings[index - 1] > ratings[index]))){
+                        count[index] = 1;
+                    } else if(((ratings[index - 1] == ratings[index]) && (ratings[index + 1] < ratings[index]))){
+                        count[index] = count[index + 1] + 1;
+                    } else if(((ratings[index + 1] == ratings[index]) && (ratings[index - 1] < ratings[index]))){
+                        count[index] = count[index - 1] + 1;
+                    }
+                    else {
+                        if(count[index - 1] > count[index + 1]){
+                            count[index] = count[index - 1] + 1;
+                        } else {
+                            count[index] = count[index + 1] + 1;
+                        }
+                    }
+                }
+            }
+        }
+        int result = 0;
+        for(int c : count){
+            result += c;
+        }
+        return result;
+    }
+}