문제 추가

Author: jdalma

longest-common-subsequence/jdalma.kt

@@ -0,0 +1,65 @@
+package leetcode_study
+
+import io.kotest.matchers.shouldBe
+import org.junit.jupiter.api.Test
+import kotlin.math.max
+
+class `longest-common-subsequence` {
+
+    fun longestCommonSubsequence(text1: String, text2: String): Int {
+        return usingDP(text1, text2)
+    }
+
+    /**
+     * TC: O(2^(n + m)), SC: O(n + m) 시간초과!!!
+     */
+    private fun usingBruteForce(text1: String, text2: String): Int {
+
+        fun dfs(i: Int, j: Int): Int =
+            if (i == text1.length || j == text2.length) 0
+            else if(text1[i] == text2[j]) 1 + dfs(i + 1, j + 1)
+            else max(dfs(i + 1, j), dfs(i, j + 1))
+
+        return dfs(0, 0)
+    }
+
+    /**
+     * TC: O(n * m), SC: O(n * m)
+     */
+    private fun usingMemoization(text1: String, text2: String): Int {
+
+        fun dfs(i: Int, j: Int, memo: Array<IntArray>): Int {
+            if (i == text1.length || j == text2.length) return 0
+            else if (memo[i][j] != -1) return memo[i][j]
+
+            memo[i][j] = if(text1[i] == text2[j]) 1 + dfs(i + 1, j + 1, memo)
+            else max(dfs(i + 1, j, memo), dfs(i, j + 1, memo))
+
+            return memo[i][j]
+        }
+        val memo = Array(text1.length) { IntArray(text2.length) { -1 } }
+        return dfs(0, 0, memo)
+    }
+
+    /**
+     * TC: O(n * m), SC: O(n * m)
+     */
+    private fun usingDP(text1: String, text2: String): Int {
+        val dp = Array(text1.length + 1) { IntArray(text2.length + 1) }
+        for (i in text1.indices) {
+            for (j in text2.indices) {
+                dp[i + 1][j + 1] = if (text1[i] == text2[j]) dp[i][j] + 1
+                else max(dp[i + 1][j], dp[i][j + 1])
+            }
+        }
+        return dp[text1.length][text2.length]
+    }
+
+    @Test
+    fun `입력받은 두 문자열의 가장 긴 공통 부분 수열의 길이를 반환하라`() {
+        longestCommonSubsequence("abcde", "ace") shouldBe 3
+        longestCommonSubsequence("abc", "abc") shouldBe 3
+        longestCommonSubsequence("abcdefghi", "defi") shouldBe 4
+        longestCommonSubsequence("abc", "def") shouldBe 0
+    }
+}