Update 316-remove-duplicate-letters.js

Author: everthis

316-remove-duplicate-letters.js

@@ -52,3 +52,27 @@ const removeDuplicateLetters = function(s) {
   }
   return String.fromCharCode(...aChNo)
 }
+
+// another
+
+/**
+ * @param {string} s
+ * @return {string}
+ */
+const removeDuplicateLetters = function(s) {
+  const last = {}
+  for (let i = 0; i < s.length; i++) last[s.charAt(i)] = i
+  const added = {}
+  const stack = []
+  for (let i = 0; i < s.length; i++) {
+    const char = s.charAt(i)
+    if (added[char]) continue
+    while (stack.length && char < stack[stack.length - 1] && last[stack[stack.length - 1]] > i) {
+      added[stack[stack.length - 1]] = false
+      stack.pop()
+    }
+    stack.push(char)
+    added[char] = true
+  }
+  return stack.join('')
+}