refactor 486

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_486.java

@@ -32,30 +32,34 @@
  */
 public class _486 {
 
-    /**credit: https://discuss.leetcode.com/topic/76312/java-1-line-recursion-solution
-     * Explanation
-     So assuming the sum of the array it SUM, so eventually player1 and player2 will split the SUM between themselves.
-     For player1 to win, he/she has to get more than what player2 gets.
-     If we think from the prospective of one player, then what he/she gains each time is a plus,
-     while, what the other player gains each time is a minus. Eventually if player1 can have a >0 total, player1 can win.
-
-     Helper function simulate this process. In each round:
-     if e==s, there is no choice but have to select nums[s]
-     otherwise, this current player has 2 options:
-     --> nums[s]-helper(nums,s+1,e): this player select the front item, leaving the other player a choice from s+1 to e
-     --> nums[e]-helper(nums,s,e-1): this player select the tail item, leaving the other player a choice from s to e-1
-     Then take the max of these two options as this player's selection, return it.*/
-    public boolean predictTheWinner(int[] nums) {
-        return helper(nums, 0, nums.length - 1, new Integer[nums.length][nums.length]) >= 0;
-    }
+    public static class Solution1 {
+        /**
+         * credit: https://discuss.leetcode.com/topic/76312/java-1-line-recursion-solution
+         * Explanation
+         * So assuming the sum of the array it SUM, so eventually player1 and player2 will split the SUM between themselves.
+         * For player1 to win, he/she has to get more than what player2 gets.
+         * If we think from the prospective of one player, then what he/she gains each time is a plus,
+         * while, what the other player gains each time is a minus. Eventually if player1 can have a >0 total, player1 can win.
+         * 
+         * Helper function simulate this process. In each round:
+         * if e==s, there is no choice but have to select nums[s]
+         * otherwise, this current player has 2 options:
+         * --> nums[s]-helper(nums,s+1,e): this player select the front item, leaving the other player a choice from s+1 to e
+         * --> nums[e]-helper(nums,s,e-1): this player select the tail item, leaving the other player a choice from s to e-1
+         * Then take the max of these two options as this player's selection, return it.
+         */
+        public boolean predictTheWinner(int[] nums) {
+            return helper(nums, 0, nums.length - 1, new Integer[nums.length][nums.length]) >= 0;
+        }
 
-    private int helper(int[] nums, int start, int end, Integer[][] mem) {
-        if (mem[start][end] == null) {
-            mem[start][end] = start == end ? nums[end] :
-                    Math.max(nums[end] - helper(nums, start, end - 1, mem),
-                            nums[start] - helper(nums, start + 1, end, mem));
+        private int helper(int[] nums, int start, int end, Integer[][] mem) {
+            if (mem[start][end] == null) {
+                mem[start][end] = start == end ? nums[end] :
+                        Math.max(nums[end] - helper(nums, start, end - 1, mem),
+                                nums[start] - helper(nums, start + 1, end, mem));
+            }
+            return mem[start][end];
         }
-        return mem[start][end];
     }
 
 }