For example: custom alphabet: xyzabc
input to sort according to custom alphabet: cyxz
output according to custom alphabet: xyzc .
因为alphabet有限，可以 bucket sort，将alph存进map，设alpg 度为m，输 度n，那么空间
O(M), 时间max(m ,n 或者直接存 26个字 表的bucket，然后找找alph的顺序输出。空间26，时间 样
解法1:
public String changeAlph(String alph, String word) {
int[] bucket = new int[26];
for (char c : word.toCharArray()) {
bucket[c - ‘a‘]++;
}
StringBuilder sb = new StringBuilder();
for (char c : alph.toCharArray()) {
while (bucket[c - ‘a‘]-- > 0) sb.append(c);
}
return sb.toString();
}
解法2:
public String changeAlph(String alph, String word) {
Map<Character, Integer> map = new HashMap<>();
for (char c : word.toCharArray()) {
if (!map.containsKey(c)) map.put(c, 0);
map.put(c, map.get(c) + 1);
}
StringBuilder sb = new StringBuilder();
for (char c : alph.toCharArray()) {
if (map.containsKey(c)) {
for (int i = 0; i < map.get(c); i++) sb.append(c);
}
}
return sb.toString();
}
