add a solution for 1423

fishercoder1534 · fishercoder1534 · commit c74e9e71cdcb · 2022-01-15T12:06:09.000-08:00
diff --git a/src/main/java/com/fishercoder/solutions/_1423.java b/src/main/java/com/fishercoder/solutions/_1423.java
@@ -21,4 +21,36 @@ public int maxScore(int[] cardPoints, int k) {
             return maxScore;
         }
     }
+
+    public static class Solution2 {
+        /**
+         * My own implementation after looking at hints on LeetCode.
+         */
+        public int maxScore(int[] cardPoints, int k) {
+            long sum = 0;
+            for (int i = 0; i < cardPoints.length; i++) {
+                sum += cardPoints[i];
+            }
+            int windowSize = cardPoints.length - k;
+            if (windowSize == 0) {
+                return (int) sum;
+            }
+            long windowSum = 0;
+            int ans = 0;
+            for (int i = 0, j = i; i < cardPoints.length - windowSize && j <= cardPoints.length + 1; ) {
+                if (j - i < windowSize) {
+                    windowSum += cardPoints[j];
+                    j++;
+                } else if (j - i == windowSize) {
+                    ans = (int) Math.max(ans, sum - windowSum);
+                    windowSum += cardPoints[j];
+                    j++;
+                } else {
+                    windowSum -= cardPoints[i];
+                    i++;
+                }
+            }
+            return (int) Math.max(ans, sum - windowSum);
+        }
+    }
 }
diff --git a/src/test/java/com/fishercoder/_1423Test.java b/src/test/java/com/fishercoder/_1423Test.java
@@ -8,17 +8,42 @@
 
 public class _1423Test {
     private static _1423.Solution1 solution1;
+    private static _1423.Solution2 solution2;
     private static int[] cardPoints;
+    private static int expected;
+    private static int k;
 
     @BeforeClass
     public static void setup() {
         solution1 = new _1423.Solution1();
+        solution2 = new _1423.Solution2();
     }
 
     @Test
     public void test1() {
         cardPoints = new int[]{1, 2, 3, 4, 5, 6, 1};
-        assertEquals(12, solution1.maxScore(cardPoints, 3));
+        expected = 12;
+        k = 3;
+        assertEquals(expected, solution1.maxScore(cardPoints, k));
+        assertEquals(expected, solution2.maxScore(cardPoints, k));
+    }
+
+    @Test
+    public void test2() {
+        cardPoints = new int[]{96, 90, 41, 82, 39, 74, 64, 50, 30};
+        expected = 536;
+        k = 8;
+        assertEquals(expected, solution1.maxScore(cardPoints, k));
+        assertEquals(expected, solution2.maxScore(cardPoints, k));
+    }
+
+    @Test
+    public void test3() {
+        cardPoints = new int[]{100, 40, 17, 9, 73, 75};
+        expected = 248;
+        k = 3;
+        assertEquals(expected, solution1.maxScore(cardPoints, k));
+        assertEquals(expected, solution2.maxScore(cardPoints, k));
     }
 
 }
