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algorithm notes: leetcode#541 reverse string ii

admin 11月 12, 2020 0

Problem

Solution

Initial thoughts

Python implementation

class :
    def reverseStr(self, s, k):
        """
        :type s: str
        :type k: int
        :rtype: str
        """
        lst = list(s)
        for s in range(0, len(s), 2*k):
            lst[s:s+k] = lst[s:s+k][::-1]
        return "".join(lst)

Java implementation

class  {
    public String reverseStr(String s, int k) {
        char[] lst = s.toCharArray();
        for(int st = 0; st < lst.length; st += 2*k){
            int i = st;
            int j = (st+k-1 < lst.length) ? (st+k-1) : (lst.length-1);
            while(i < j){
                char temp = lst[j];
                lst[j] = lst[i];
                lst[i] = temp;
                i++;
                j--;
            }
        }
        return new String(lst);
    }
}

Time complexity

O(n).

Space complexity

O(n).

Links

541. Reverse String II
(中文版) 算法笔记: 力扣#541 反转字符串 II