【LeetCode程序员面试金典】面试题 01.01. Is Unique LCCI

class Solution {
    public boolean isUnique(String astr) {
        boolean[] num = new boolean[26];
        Arrays.fill(num,true);
        for(int i = 0;i < astr.length();i++){
            if (num[astr.charAt(i)-'a'] == true){
                num[astr.charAt(i)-'a'] = false;
            }else{
                return false;
            }
        }
        return true;
    }
}

class Solution {
    public boolean isUnique(String astr) {
        int mark = 0;
        for(int i = 0;i < astr.length();i++){
            int bit = 1 << (astr.charAt(i) - 'a');
            if ((mark & bit) == 0) {
                mark |= bit;
            } else {
                return false;
            }
        }
        return true;
    }
}

class Solution {
    public boolean isUnique(String astr) {
        Set set = new HashSet();
        for (int i = 0; i <astr.length() ; i++) {
            set.add(astr.charAt(i));
        }
        return set.size() == astr.length(); 
    }
}

作者：evelynnnnn
链接：https://leetcode-cn.com/problems/is-unique-lcci/solution/javali-yong-setqu-zhong-by-evelynnnnn/
来源：力扣（LeetCode）
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