풀이1: Decode Ways #268

Author: seungseung88

decode-ways/seungseung88.js

@@ -0,0 +1,26 @@
+/**
+ * 시간 복잡도: O(n)
+ * 공간 복잡도: O(n)
+ */
+var numDecodings = function (s) {
+  const memo = new Map();
+  memo.set(s.length, 1);
+
+  function dfs(start) {
+    if (memo.has(start)) {
+      return memo.get(start);
+    }
+
+    if (s[start] === '0') {
+      memo.set(start, 0);
+    } else if (start + 1 < s.length && parseInt(s.slice(start, start + 2)) < 27) {
+      memo.set(start, dfs(start + 1) + dfs(start + 2));
+    } else {
+      memo.set(start, dfs(start + 1));
+    }
+
+    return memo.get(start);
+  }
+
+  dfs(0);
+};