1+ package medium
2+ 3+ import GreedyTopic
4+ import StackTopic
5+ import StringTopic
6+ import java.util.*
7+ 8+ /* *
9+ * 316. Remove Duplicate Letters
10+ * https://leetcode.com/problems/remove-duplicate-letters/
11+ *
12+ Given a string s, remove duplicate letters so that every letter appears once and only once.
13+ You must make sure your result is the smallest in lexicographical order among all possible results.
14+ BULLSHIT
15+ */
16+ 17+ class Medium316 : StringTopic , StackTopic , GreedyTopic {
18+ 19+ fun removeDuplicateLetters (s : String ): String {
20+ val stack = Stack <Char >()
21+ val freq = IntArray (26 )
22+ val seen = BooleanArray (26 )
23+ for (element in s) { freq[element - ' a' ++ }
24+ for (element in s) {
25+ freq[element - ' a' --
26+ if (seen[element - ' a' continue
27+ while (stack.size > 0 && stack.peek() > element && freq[stack.peek() - ' a' > 0 ) {
28+ seen[stack.pop() - ' a' = false
29+ }
30+ stack.push(element)
31+ seen[element - ' a' = true
32+ }
33+ return stack.joinToString(" "
34+ }
35+ }
36+ 37+ fun main () {
38+ println (Medium316 ().removeDuplicateLetters(" bcabc"
39+ println (Medium316 ().removeDuplicateLetters(" cbacdcbc"
40+ }
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