add Word Break solution

Author: HoonDongKang

word-break/HoonDongKang.ts

@@ -0,0 +1,51 @@
+/**
+ * [Problem]: [139] Word Break
+ * (https://leetcode.com/problems/word-break/description/)
+ */
+function wordBreak(s: string, wordDict: string[]): boolean {
+    //시간복잡도: O(n^2)
+    //공간복잡도: O(n)
+    function dfsFunc(s: string, wordDict: string[]): boolean {
+        let wordSet = new Set(wordDict);
+        let memo = new Map<number, boolean>();
+
+        function dfs(start: number): boolean {
+            if (start === s.length) return true;
+            if (memo.has(start)) return memo.get(start)!;
+
+            for (let end = start + 1; end <= s.length; end++) {
+                const word = s.slice(start, end);
+
+                if (wordSet.has(word) && dfs(end)) {
+                    memo.set(start, true);
+                    return true;
+                }
+            }
+
+            memo.set(start, false);
+            return false;
+        }
+
+        return dfs(0);
+    }
+
+    //시간복잡도: O(n^2)
+    //공간복잡도: O(n)
+    function dpFunc(s: string, wordDict: string[]): boolean {
+        const wordSet = new Set(wordDict);
+        const dp = new Array(s.length + 1).fill(false);
+        dp[0] = true;
+
+        for (let end = 1; end <= s.length; end++) {
+            for (let start = 0; start < end; start++) {
+                const isExists = wordSet.has(s.slice(start, end));
+                if (isExists && dp[start]) {
+                    dp[end] = true;
+                    break;
+                }
+            }
+        }
+        return dp[s.length];
+    }
+    return dpFunc(s, wordDict);
+}