Leetcode 赎金信

利用hash map做
java solution

class Solution {public boolean canConstruct(String ransomNote, String magazine) {//首先利用HashMap统计magazine中字符频率HashMap<Character, Integer> magazinefreq = new HashMap<>();for(char c : magazine.toCharArray()) {magazinefreq.put(c, magazinefreq.getOrDefault(c, 0) + 1);}for(char c : ransomNote.toCharArray()) {//如果magazine中都不存在c或者c被用完了if(!magazinefreq.containsKey(c) || magazinefreq.get(c) == 0) {return false;}magazinefreq.put(c, magazinefreq.get(c) - 1);}return true;}
}