kt: add «140. Word Break II»

Signed-off-by: Matej Focko <me@mfocko.xyz>

kt/word-break-ii.kt

@@ -0,0 +1,59 @@
+class Solution {
+    private fun precomputeFrom(
+        words: List<String>,
+        s: String,
+        dp: Map<Int, List<String>>,
+        start: Int,
+    ): List<String> {
+        val valid = mutableListOf<String>()
+
+        (start..<s.length)
+            .map { end -> end to s.substring(start..end) }
+            .filter { (_, word) -> words.contains(word) }
+            .forEach { (end, word) ->
+                when {
+                    end == s.length - 1 -> valid.add(word)
+                    else -> {
+                        dp[end + 1]?.forEach { suffix ->
+                            valid.add("$word $suffix")
+                        }
+                    }
+                }
+            }
+
+        return valid
+    }
+
+    fun wordBreak(
+        s: String,
+        wordDict: List<String>,
+    ): List<String> {
+        val dp = mutableMapOf<Int, List<String>>()
+
+        s.indices.reversed().forEach { start ->
+            dp[start] = precomputeFrom(wordDict, s, dp, start)
+        }
+
+        return dp.getOrDefault(0, emptyList())
+    }
+}
+
+fun main() {
+    val s = Solution()
+
+    check(
+        s.wordBreak("catsanddog", listOf("cat", "cats", "and", "sand", "dog")).sorted() ==
+            listOf(
+                "cats and dog", "cat sand dog",
+            ).sorted(),
+    )
+    check(
+        s.wordBreak("pineapplepenapple", listOf("apple", "pen", "applepen", "pine", "pineapple")).sorted() ==
+            listOf(
+                "pine apple pen apple", "pineapple pen apple", "pine applepen apple",
+            ).sorted(),
+    )
+    check(
+        s.wordBreak("catsandog", listOf("cats", "dog", "sand", "and", "cat")) == emptyList<String>(),
+    )
+}