LintCode: Unique Characters

C++,

time: O(n^2)

space: O(0)

class Solution {
public:
    /**
     * @param str: a string
     * @return: a boolean
     */
    bool isUnique(string &str) {
        // write your code here
        for (int i=; i<str.size(); i++) {
            for (int j=i+; j<str.size(); j++) {
                if (str[i] == str[j]) {
                    return false;
                }
            }
        }
        return true;
    }
};

C++,

time: O(n)

space: O(n)

 class Solution {
 public:
     /**
      * @param str: a string
      * @return: a boolean
      */
     bool isUnique(string &str) {
         // write your code here
         string tmp;
         for (int i=; i<str.size(); i++) {
             if (- == tmp.find(str[i])) {
                 tmp.push_back(str[i]);
             } else {
                 return false;
             }
         }
         return true;
     }
 };