LeetCode 541. Reverse String II (反转字符串 II)
Given a string and an integer k, you need to reverse the first k characters for every 2k characters counting from the start of the string. If there are less than k characters left, reverse all of them. If there are less than 2k but greater than or equal to k characters, then reverse the first k characters and left the other as original.
题目标签:String
Example:
Input: s = "abcdefg", k = 2 Output: "bacdfeg"
Restrictions:
- The string consists of lower English letters only.
- Length of the given string and k will in the range [1, 10000]
题目标签:String
今天登陆突然发现LeetCode 有中文版本了- -,再也不用纠结于 如何翻译题目名字了。
题目给了我们一个string s 和 int k,让我们每次在2k 个 chars 里只反转 k 个chars。
利用Reverse String 里的 two pointers 来反转k 个chars,每一次增加 i by 2*k 就可以了。
具体请看code。
Java Solution:
Runtime beats 67.31%
完成日期:04/07/2018
关键词:two pointers
关键点:swap left and right chars
1 class Solution 2 { 3 public String reverseStr(String s, int k) 4 { 5 char [] c_arr = s.toCharArray(); 6 7 for(int i=0; i<c_arr.length; i=i+2*k) 8 { 9 int left = i; 10 int right = Math.min(i + k - 1, c_arr.length - 1); 11 12 while(left < right) 13 { 14 // swap char 15 char temp = c_arr[left]; 16 c_arr[left] = c_arr[right]; 17 c_arr[right] = temp; 18 19 left++; 20 right--; 21 } 22 23 } 24 25 return new String(c_arr); 26 } 27 }
参考资料:n/a
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