LeetCode 344 Reverse String
Write a function that takes a string as input and returns the string reversed.
Example 1:
Input: "hello"
Output: "olleh"
Example 2:
Input: "A man, a plan, a canal: Panama"
Output: "amanaP :lanac a ,nalp a ,nam A"
1 //方法一：用StringBuilder， Time： O(n), Space: O(n) 2 public String reverseString(String s) { 3 if (s == null || s.length() == 0) { 4 return s; 5 } 6 7 StringBuilder sb = new StringBuilder(); 8 9 for(int i = s.length() - 1; i >= 0; i--) { 10 sb.append(s.charAt(i)); 11 } 12 13 return sb.toString(); 14 } 15 16 17 //方法二：用array， Time： O(n), Space: O(n) 18 public String reverseString(String s) { 19 if (s == null || s.length() == 0) { 20 return s; 21 } 22 23 char[] result = s.toCharArray(); 24 int i = 0; 25 int j = result.length - 1; 26 27 while (i < j) { 28 swap(i, j, result); 29 i++; 30 j--; 31 } 32 33 return new String(result);//最后要把array再转回string 34 } 35 36 public void swap(int i, int j, char[] c) { 37 char temp = c[i]; 38 c[i] = c[j]; 39 c[j] = temp; 40 }
