Space-optimized solution to "Maximum Score After Splitting a String" …

…problem
dkoval · Jan 1, 2025 · 717e2ad · 717e2ad
1 parent 2fae1fd
commit 717e2ad
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diff --git a/src/main/java/com/github/dkoval/leetcode/challenge/MaximumScoreAfterSplittingString.java b/src/main/java/com/github/dkoval/leetcode/challenge/MaximumScoreAfterSplittingString.java
@@ -78,4 +78,32 @@ public int maxScore(String s) {
             return best;
         }
     }
+
+    // O(N) time | O(1) space
+    class MaximumScoreAfterSplittingStringRev3 implements MaximumScoreAfterSplittingString {
+
+        @Override
+        public int maxScore(String s) {
+            final var n = s.length();
+
+            var rightOnes = 0;
+            for (var i = 0; i < n; i++) {
+                if (s.charAt(i) == '1') {
+                    rightOnes++;
+                }
+            }
+
+            var best = 0;
+            var leftZeros = 0;
+            for (var i = 0; i < n - 1; i++) {
+                if (s.charAt(i) == '0') {
+                    leftZeros++;
+                } else {
+                    rightOnes--;
+                }
+                best = Math.max(best, leftZeros + rightOnes);
+            }
+            return best;
+        }
+    }
 }
diff --git a/src/test/kotlin/com/github/dkoval/leetcode/challenge/MaximumScoreAfterSplittingStringTest.kt b/src/test/kotlin/com/github/dkoval/leetcode/challenge/MaximumScoreAfterSplittingStringTest.kt
@@ -1,7 +1,6 @@
 package com.github.dkoval.leetcode.challenge
 
-import com.github.dkoval.leetcode.challenge.MaximumScoreAfterSplittingString.MaximumScoreAfterSplittingStringRev1
-import com.github.dkoval.leetcode.challenge.MaximumScoreAfterSplittingString.MaximumScoreAfterSplittingStringRev2
+import com.github.dkoval.leetcode.challenge.MaximumScoreAfterSplittingString.*
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Nested
 import org.junit.jupiter.api.extension.ExtensionContext
@@ -48,6 +47,19 @@ internal class MaximumScoreAfterSplittingStringTest {
             MaximumScoreAfterSplittingStringRev2().test(s, expected)
         }
     }
+
+    @Nested
+    inner class MaximumScoreAfterSplittingStringRev3Test {
+
+        @ParameterizedTest
+        @ArgumentsSource(InputArgumentsProvider::class)
+        fun `should return the maximum score after splitting the string into two non-empty substrings`(
+            s: String,
+            expected: Int
+        ) {
+            MaximumScoreAfterSplittingStringRev3().test(s, expected)
+        }
+    }
 }
 
 private fun MaximumScoreAfterSplittingString.test(s: String, expected: Int) {