LF.281.Remove Spaces

 1 public String removeSpaces(String input) {
 2         // Write your solution here
 3         //corner case
 4         if (input.isEmpty()){
 5             return input ;
 6         }
 7         /*
 8         return [0, i) j is the counter
 9         * case 1: not space: input[i++] = input[j++]
10         * case 2: if space
11         *         2.1: leading space: skip
12         *         i = 0
13         *         2.2: duplicate space: keep the first space
14         *         j != j-1 : j一定是SPACE, J-1 如果不是的话，把当前的SPACE 给I 吃
15         *         2.3: trailing space : remove
16         *         j to the end, and i = "", i--
17         * */
18         int slow = 0, fast = 0;
19         char[] chars = input.toCharArray();
20         while (fast < chars.length){
21             if (chars[fast] !=‘ ‘ ){
22                 chars[slow++] = chars[fast++] ;
23             } else{
24                 //非开头， 中间没连续_ 末尾可能进去一个 _
25                 if (slow>0 && chars[fast] != chars[fast-1]){
26                     chars[slow++] = chars[fast++] ;
27                 } else{
28                     fast++ ;
29                 }
30             }
31         }
32         //post-processing: it is possible we still have one trailing ‘ ‘
33         if (slow>0 && chars[slow-1] == ‘ ‘){
34             return new String(chars, 0, slow-1) ;
35         }
36         return new String(chars, 0, slow) ;
37     }