CC150 1.1 字符串查唯一bit manipulation详解

    public boolean isUniqueChars2(String str) {
        int checker = 0;
        for (int i = 0; i < str.length(); i++) { 
            int val = str.charAt(i) - ‘a‘; //保证val的值不超过26
            if ((checker & (1 << val)) > 0) {
                return false;
            } else {
                checker |= (1 << val);//checker=checker | (1<<val)
            }
        }
        return true;
    }