6주차 답안 제출

Author: jdalma

container-with-most-water/jdalma.kt

@@ -0,0 +1,40 @@
+package leetcode_study
+
+import io.kotest.matchers.shouldBe
+import org.junit.jupiter.api.Test
+import kotlin.math.abs
+import kotlin.math.max
+import kotlin.math.min
+
+typealias Element = Pair<Int,Int>
+
+class `container-with-most-wate` {
+
+    /**
+     * 투 포인터를 활용하여 높이가 낮은 인덱스의 값을 한 칸씩 이동하며 최대 높이를 반환한다.
+     * TC: O(n), SC: O(1)
+     */
+    fun maxArea(height: IntArray): Int {
+        var (left, right) = 0 to height.size - 1
+        var result = 0
+
+        while (left < right) {
+            result = max(result, extent(Element(height[left], left), Element(height[right], right)))
+            if (height[left] < height[right]) {
+                left++
+            } else {
+                right--
+            }
+        }
+        return result
+    }
+
+    private fun extent(e1: Element, e2: Element): Int {
+        return min(e1.first, e2.first) * abs(e1.second - e2.second)
+    }
+
+    @Test
+    fun `입력받은 높이를 표현하는 정수 배열에서 받을 수 있는 최대의 물의 양을 반환한다`() {
+        maxArea(intArrayOf(1,8,6,2,5,4,8,3,7)) shouldBe 49
+    }
+}

design-add-and-search-words-data-structure/jdalma.kt

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+package leetcode_study
+
+import io.kotest.matchers.shouldBe
+import leetcode_study.Type.*
+import org.junit.jupiter.api.Test
+
+class `design-add-and-search-words-data-structure` {
+
+    class Node {
+        var isEnd: Boolean = false
+        val next: MutableMap<Char, Node> = mutableMapOf()
+    }
+
+    class WordDictionary {
+        private val root = Node()
+
+        /**
+         * TC: O(n), SC: O(n)
+         */
+        fun addWord(word: String) {
+            var now = root
+
+            for (index in word.indices) {
+                val node =
+                    if (now.next.containsKey(word[index])) { now.next[word[index]] }
+                    else Node().also { now.next[word[index]] = it }
+                node?.let { now = it }
+            }
+            now.isEnd = true
+        }
+
+        /**
+         * TC: O(26^n), SC: O(n)
+         */
+        fun search(word: String): Boolean {
+
+            fun dfs(node: Node, word: String, index: Int): Boolean {
+                return if (index == word.length) node.isEnd
+                else if (word[index] == '.') {
+                    node.next.values.any { dfs(it, word, index + 1) }
+                }
+                else {
+                    node.next[word[index]]?.let { dfs(it, word, index + 1) } ?: false
+                }
+            }
+
+            return dfs(this.root, word, 0)
+        }
+    }
+
+    @Test
+    fun `문자열을 저장하고 검색하는 자료구조를 구현하라`() {
+        inputCommands(
+            Command(ADD, "bad"),
+            Command(ADD, "dad"),
+            Command(ADD, "mad"),
+            Command(SEARCH, "pad", false),
+            Command(SEARCH, "bad", true),
+            Command(SEARCH, ".ad", true),
+            Command(SEARCH, "b..", true),
+        )
+        inputCommands(
+            Command(ADD, "at"),
+            Command(ADD, "and"),
+            Command(ADD, "an"),
+            Command(ADD, "add"),
+            Command(SEARCH, "a", false),
+            Command(SEARCH, ".at", false),
+            Command(ADD, "bat"),
+            Command(SEARCH,".at", true),
+            Command(SEARCH,"an.", true),
+            Command(SEARCH,"a.d.", false),
+            Command(SEARCH,"b.", false),
+            Command(SEARCH,"a.d", true),
+            Command(SEARCH,".",  false)
+        )
+    }
+
+    private fun inputCommands(vararg commands: Command) {
+        val dictionary = WordDictionary()
+        for (command in commands) {
+            when(command.type) {
+                ADD -> dictionary.addWord(command.word)
+                SEARCH -> dictionary.search(command.word) shouldBe command.expect
+            }
+        }
+    }
+}
+
+data class Command(
+    val type: Type,
+    val word: String,
+    val expect : Boolean? = null
+)
+
+enum class Type {
+    ADD, SEARCH;
+}

valid-parentheses/jdalma.kt

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+package leetcode_study
+
+import io.kotest.matchers.shouldBe
+import org.junit.jupiter.api.Test
+import java.util.Deque
+import java.util.ArrayDeque
+
+class `valid-parentheses` {
+
+    /**
+     * 괄호의 쌍을 Stack을 활용하여 검증한다.
+     * TC: O(n), SC: O(n)
+     */
+    fun isValid(s: String): Boolean {
+        if (s.length % 2 != 0) return false
+        val parentheses = mapOf(
+            '(' to ')',
+            '{' to '}',
+            '[' to ']'
+        )
+
+        val stack: Deque<Char> = ArrayDeque()
+        for (char in s) {
+            if (parentheses.containsKey(char)) {
+                stack.push(char)
+            } else if (stack.isEmpty() || parentheses[stack.pop()] != char){
+                return false
+            }
+        }
+        return stack.isEmpty()
+    }
+
+    @Test
+    fun `입력한 문자열의 괄호의 열림과 닫힘을 검증한다`() {
+        isValid("()") shouldBe true
+        isValid("{()}") shouldBe true
+        isValid("(){}[]") shouldBe true
+
+        isValid("{(}") shouldBe false
+        isValid("){") shouldBe false
+    }
+}