剑指 Offer 58 - II. 左旋转字符串

剑指 Offer 58 - II. 左旋转字符串

class Solution {
    public String reverseLeftWords(String s, int n) {
        if (s == null)
            return null;
        char[] str = s.toCharArray();
        n %= s.length();
        reverse(str, 0, s.length() - 1);
        reverse(str, 0, s.length() - 1 - n);
        reverse(str, s.length() - n, s.length() - 1);
        return new String(str);
    }
    private void reverse(char[] str, int start, int end) {
        while (start < end) {
            char temp = str[start];
            str[start] = str[end];
            str[end] = temp;
            ++start;
            --end;
        }
    }
}