|
1 | 1 | classSolution { |
2 | | -publicStringremoveDuplicateLetters(Strings) { |
3 | | -int[]counter =newint[26]; |
4 | | -for (charc :s.toCharArray()) { |
5 | | -counter[c -'a']++; |
| 2 | +publicStringremoveDuplicateLetters(Strings) { |
| 3 | +Map<Character,Integer>lastIndexMap =newHashMap<>(); |
| 4 | +for (inti =0;i <s.length();i++) { |
| 5 | +lastIndexMap.put(s.charAt(i),i); |
| 6 | + } |
| 7 | +Stack<Character>stack =newStack<>(); |
| 8 | +Set<Character>visited =newHashSet<>(); |
| 9 | +for (inti =0;i <s.length();i++) { |
| 10 | +charc =s.charAt(i); |
| 11 | +if (!visited.contains(c)) { |
| 12 | +while (!stack.isEmpty() &&c <stack.peek() &&lastIndexMap.get(stack.peek()) >i) { |
| 13 | +visited.remove(stack.pop()); |
| 14 | + } |
| 15 | +visited.add(c); |
| 16 | +stack.push(c); |
| 17 | + } |
| 18 | + } |
| 19 | +StringBuildersb =newStringBuilder(); |
| 20 | +for (Characterc :stack) { |
| 21 | +sb.append(c); |
| 22 | + } |
| 23 | +returnsb.toString(); |
6 | 24 | } |
7 | | -Stack<Integer>stack =newStack<>(); |
8 | | -boolean[]visited =newboolean[26]; |
9 | | -for (charc :s.toCharArray()) { |
10 | | -intidx =c -'a'; |
11 | | -counter[idx]--; |
12 | | -if (visited[idx]) { |
13 | | -continue; |
14 | | - } |
15 | | -while (!stack.isEmpty() &&stack.peek() >idx &&counter[stack.peek()] >0) { |
16 | | -visited[stack.pop()] =false; |
17 | | - } |
18 | | -stack.add(idx); |
19 | | -visited[idx] =true; |
20 | | - } |
21 | | -StringBuildersb =newStringBuilder(); |
22 | | -while (!stack.isEmpty()) { |
23 | | -sb.append((char) (stack.pop() +'a')); |
24 | | - } |
25 | | -returnsb.reverse().toString(); |
26 | | - } |
27 | 25 | } |