題目

解答

class Solution {public char kthCharacter(int k) {int n = 0;int v = 1;while (v < k) {v <<= 1;++n;}String target = kthCharacterString(n);return target.charAt(k - 1);}public String kthCharacterString(int n) {if (n == 0) {return "a";}String v = kthCharacterString(n - 1);StringBuilder sb = new StringBuilder();sb.append(v);for (int i = 0; i < v.length(); ++i) {char c1 = v.charAt(i);char c2 = (char) (c1 + 1);if (c1 == 'z') {c2 = 'a';}sb.append(c2);}return sb.toString();}
}

總結
依據規則，得到目標字符串，然后獲取目標位置的字符，算是暴力解題。