Create 0135-candy.kt

Author: a93a

kotlin/0135-candy.kt

@@ -0,0 +1,64 @@
+// O(n) linear sweep solution
+class Solution {
+    fun candy(ratings: IntArray): Int {
+        val n = ratings.size
+        val candies = IntArray (n) { 1 }
+
+        for (i in 1 until n) {
+            if (ratings[i] > ratings[i - 1])
+                candies[i] = candies[i - 1] + 1
+        }
+
+        for (i in n - 2 downTo 0){
+            if (ratings[i] > ratings[i + 1])
+                candies[i] = max(candies[i], candies[i + 1] + 1)
+        }
+
+        return candies.sum() ?: n
+    }
+
+//graph dfs solution
+class Solution {
+    fun candy(ratings: IntArray): Int {
+        val n = ratings.size
+        val outdegree = IntArray (n)
+
+        for (i in 0 until n) {
+            if (i > 0 && ratings[i] > ratings[i - 1])
+                outdegree[i]++
+            if (i + 1 < n && ratings[i] > ratings[i + 1])
+                outdegree[i]++
+        }
+
+        val q = LinkedList<Int>()
+        for ((index, degree) in outdegree.withIndex()) {
+            if (degree == 0)
+                q.addLast(index)
+        }
+
+        val candies = IntArray (n)
+        while (q.isNotEmpty()) {
+            val i = q.removeFirst()
+
+            var candy = 1
+            if (i > 0 && ratings[i] > ratings[i - 1])
+                candy = maxOf(candy, candies[i - 1] + 1)
+            if (i < n - 1 && ratings[i] > ratings[i + 1])
+                candy = maxOf(candy, candies[i + 1] + 1)
+            candies[i] = candy
+
+            if (i > 0 && ratings[i] < ratings[i - 1]) {
+                outdegree[i - 1]--
+                if (outdegree[i - 1] == 0)
+                    q.addLast(i - 1)
+            }
+            if (i < n - 1 && ratings[i] < ratings[i + 1]) {
+                outdegree[i + 1]--
+                if (outdegree[i + 1] == 0)
+                    q.addLast(i + 1)
+            }
+        }
+
+        return candies.sum()!!
+    }
+}