2914: calculate the minimum number of changes to make a binary String beautiful

Author: emanuelschmoczer

README.md

@@ -4,18 +4,19 @@ My solutions to LeetCode problems in Kotlin.
 
 ## Solutions
 
-|                                 #                                  |                                                    Title                                                     | Difficulty |
-|:------------------------------------------------------------------:|:------------------------------------------------------------------------------------------------------------:|:----------:|
-|      [1](https://leetcode.com/problems/two-sum/description/)       |                      [Two Sum](src/main/kotlin/com/schmoczer/leetcode/_0001/TwoSum.kt)                       |    Easy    |
-| [5](https://leetcode.com/problems/longest-palindromic-substring/)  | [Longest Palindromic Substring](src/main/kotlin/com/schmoczer/leetcode/_0005/LongestPalindromicSubstring.kt) |   Medium   |
-|     [8](https://leetcode.com/problems/string-to-integer-atoi/)     |         [String to Integer (atoi)](src/main/kotlin/com/schmoczer/leetcode/_0008/StringToInteger.kt)          |   Medium   |
-|       [20](https://leetcode.com/problems/valid-parentheses/)       |            [Valid Parentheses](src/main/kotlin/com/schmoczer/leetcode/_0020/ValidParentheses.kt)             |    Easy    |
-|        [49](https://leetcode.com/problems/group-anagrams/)         |               [Group Anagrams](src/main/kotlin/com/schmoczer/leetcode/_0049/GroupAnagrams.kt)                |   Medium   |
-|       [125](https://leetcode.com/problems/valid-palindrome/)       |             [Valid Palindrome](src/main/kotlin/com/schmoczer/leetcode/_0125/ValidPalindrome.kt)              |    Easy    |
-|  [151](https://leetcode.com/problems/reverse-words-in-a-string/)   |      [Reverse Words in a String](src/main/kotlin/com/schmoczer/leetcode/_0151/ReverseWordsInString.kt)       |   Medium   |
-| [186](https://leetcode.com/problems/reverse-words-in-a-string-ii/) | [Reverse Words in a String II](src/main/kotlin/com/schmoczer/leetcode/_0186/ReverseWordsInStringInPlace.kt)  |   Medium   |
-|     [206](https://leetcode.com/problems/reverse-linked-list/)      |           [Reverse Linked List](src/main/kotlin/com/schmoczer/leetcode/_0206/ReverseLinkedList.kt)           |    Easy    |
-|        [344](https://leetcode.com/problems/reverse-string/)        |               [Reverse String](src/main/kotlin/com/schmoczer/leetcode/_0344/ReverseString.kt)                |    Easy    |
-|        [796](https://leetcode.com/problems/rotate-string/)         |                [Rotate String](src/main/kotlin/com/schmoczer/leetcode/_0796/RotateString.kt)                 |    Easy    |
-|      [2490](https://leetcode.com/problems/circular-sentence/)      |            [Circular Sentence](src/main/kotlin/com/schmoczer/leetcode/_2490/CircularSentence.kt)             |    Easy    |
-|   [3163](https://leetcode.com/problems/string-compression-iii/)    |         [String Compression III](src/main/kotlin/com/schmoczer/leetcode/_3163/StringCompression3.kt)         |   Medium   |
+|                                                #                                                 |                                                          Title                                                          | Difficulty |
+|:------------------------------------------------------------------------------------------------:|:-----------------------------------------------------------------------------------------------------------------------:|:----------:|
+|                     [1](https://leetcode.com/problems/two-sum/description/)                      |                            [Two Sum](src/main/kotlin/com/schmoczer/leetcode/_0001/TwoSum.kt)                            |    Easy    |
+|                [5](https://leetcode.com/problems/longest-palindromic-substring/)                 |      [Longest Palindromic Substring](src/main/kotlin/com/schmoczer/leetcode/_0005/LongestPalindromicSubstring.kt)       |   Medium   |
+|                    [8](https://leetcode.com/problems/string-to-integer-atoi/)                    |               [String to Integer (atoi)](src/main/kotlin/com/schmoczer/leetcode/_0008/StringToInteger.kt)               |   Medium   |
+|                      [20](https://leetcode.com/problems/valid-parentheses/)                      |                  [Valid Parentheses](src/main/kotlin/com/schmoczer/leetcode/_0020/ValidParentheses.kt)                  |    Easy    |
+|                       [49](https://leetcode.com/problems/group-anagrams/)                        |                     [Group Anagrams](src/main/kotlin/com/schmoczer/leetcode/_0049/GroupAnagrams.kt)                     |   Medium   |
+|                      [125](https://leetcode.com/problems/valid-palindrome/)                      |                   [Valid Palindrome](src/main/kotlin/com/schmoczer/leetcode/_0125/ValidPalindrome.kt)                   |    Easy    |
+|                 [151](https://leetcode.com/problems/reverse-words-in-a-string/)                  |            [Reverse Words in a String](src/main/kotlin/com/schmoczer/leetcode/_0151/ReverseWordsInString.kt)            |   Medium   |
+|                [186](https://leetcode.com/problems/reverse-words-in-a-string-ii/)                |       [Reverse Words in a String II](src/main/kotlin/com/schmoczer/leetcode/_0186/ReverseWordsInStringInPlace.kt)       |   Medium   |
+|                    [206](https://leetcode.com/problems/reverse-linked-list/)                     |                [Reverse Linked List](src/main/kotlin/com/schmoczer/leetcode/_0206/ReverseLinkedList.kt)                 |    Easy    |
+|                       [344](https://leetcode.com/problems/reverse-string/)                       |                     [Reverse String](src/main/kotlin/com/schmoczer/leetcode/_0344/ReverseString.kt)                     |    Easy    |
+|                       [796](https://leetcode.com/problems/rotate-string/)                        |                      [Rotate String](src/main/kotlin/com/schmoczer/leetcode/_0796/RotateString.kt)                      |    Easy    |
+|                     [2490](https://leetcode.com/problems/circular-sentence/)                     |                  [Circular Sentence](src/main/kotlin/com/schmoczer/leetcode/_2490/CircularSentence.kt)                  |    Easy    |
+| [2914](https://leetcode.com/problems/minimum-number-of-changes-to-make-binary-string-beautiful/) | [Minimum Number of Changes to Make Binary String Beautiful](src/main/kotlin/com/schmoczer/leetcode/_2914/MinChanges.kt) |   Medium   |
+|                  [3163](https://leetcode.com/problems/string-compression-iii/)                   |              [String Compression III](src/main/kotlin/com/schmoczer/leetcode/_3163/StringCompression3.kt)               |   Medium   |

src/main/kotlin/com/schmoczer/leetcode/_2914/MinChanges.kt

@@ -0,0 +1,14 @@
+package com.schmoczer.leetcode._2914
+
+class MinChanges {
+    fun minChanges(s: String): Int {
+        var changes = 0
+        for (i in 2..s.length step 2) {
+            val part = s.substring(i - 2, i)
+            if (part == "01" || part == "10") {
+                changes++
+            }
+        }
+        return changes
+    }
+}

src/main/kotlin/com/schmoczer/leetcode/_2914/README.md

@@ -0,0 +1,36 @@
+# Minimum Number of Changes to Make Binary String Beautiful
+
+You are given a 0-indexed binary string `s` having an even length.
+
+A string is beautiful if it's possible to partition it into one or more substrings such that:
+
+- Each substring has an even length.
+- Each substring contains only `1`'s or only `0`'s.
+
+You can change any character in `s` to `0` or `1`.
+
+Return the minimum number of changes required to make the string `s` beautiful.
+
+Example 1:
+
+> Input: s = "1001"
+>
+> Output: 2
+
+Example 2:
+
+> Input: s = "10"
+>
+> Output: 1
+
+Example 3:
+
+> Input: s = "0000"
+>
+> Output: 0
+
+Constraints:
+
+- `2 <= s.length <= 105`
+- `s` has an even length.
+- `s[i]` is either `'0'` or `'1'`.

src/test/kotlin/com/schmoczer/leetcode/_2914/MinChangesTest.kt

@@ -0,0 +1,29 @@
+package com.schmoczer.leetcode._2914
+
+import org.junit.jupiter.api.BeforeEach
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class MinChangesTest {
+    private lateinit var sut: MinChanges
+
+    @BeforeEach
+    fun setUp() {
+        sut = MinChanges()
+    }
+
+    @Test
+    fun `1001 needs 2 changes`() {
+        assertEquals(2, sut.minChanges("1001"))
+    }
+
+    @Test
+    fun `10 nees 1 change`() {
+        assertEquals(1, sut.minChanges("10"))
+    }
+
+    @Test
+    fun `0000 needs 0 changes`() {
+        assertEquals(0, sut.minChanges("0000"))
+    }
+}