[cc150] 1.3

 Design an algorithm and write code to remove the duplicate characters in a string without using any additional buffer. NOTE: One or two additional variables are fine. An extra copy of the array is not.

FOLLOW UP

Write the test cases for this method.

如果可以使用O(1)的空间的话，就用个naive的hash来做吧

class Solution {
public:
    void removeDuplicates(char *str){
        vector<bool> exist(256, 0);
        char *p = str;
        int cnt = 0;
        while (*p) {
            if(exist[*p]){
                cnt++;
            }else{
                exist[*p] = 1;
                *(p-cnt) = *p;
            }

            p++;
        }
        p--;
        for (int i = 0; i < cnt; i++) {
            *(p-i) = 0;
        }
    }
};

如果不可以的话，那就排序O(nlogn)再做

如果连排序都不行的话，只能O(n^2)了