亚麻：2018-1 find K distinct substring without duplication

 

这是亚麻2018 年新题的第一题：

 

// find K distinct substring whithout duplication

#include <iostream>     // std::cout

#include <algorithm>    // std::make_heap, std::pop_heap, std::push_heap, std::sort_heap

#include <vector>       // std::vector

#include <unordered_map>

#include <unordered_set>

#include <numeric>

#include <sys/time.h>

 

//solution:

//data structure: slide window and hashmap.

//algorithm:use slide window<sp , ep> to mark each substring and check if the substring have duplicted character.

//use the hash map<char , int > check if the substring have duplicated character. if no,  and it is not in res, then load it into res.

//iterate all substring. so the comlexity is c(n).

 

using namespace std;

 

std::vector<string> subStringKDistinct(string& str, int K){

    int s =0;

    int e = K;

    unordered_map<char, int> hashmap;  // use to check if the susbtring have duplicated character.

    vector<string> res;   // load the findings.

    

    while (e <= str.size()){

        hashmap.clear();

        

        //check if there is duplicated char in the slided window by hashtable.

        for ( int p = s; p < e; p++){

            hashmap[str[p]] += 1;

        }

        

        for (auto& e: hashmap){

            if (e.second >= 2){  // check duplicated character. if having duplicate char. do not meet the requirement.

                goto CONTINUE;

            }

        }

        

        //check if duplicate using == of two substring. comparing with the hashtable, the effeciency is almost same.

        for (auto& e: res){

            if (e == str.substr(s,K))

                goto CONTINUE;

        }

        res.push_back(str.substr(s, K));

        

    CONTINUE:  //move the slide window.

        s++;

        e++;

    }

    return res;

}

 

 

int main () {

    

    struct timeval tv;

    gettimeofday(&tv,NULL);

    long ts = tv.tv_sec * 1000 + tv.tv_usec / 1000;

    

    

    string s ={"awaglknagawunagwkwagl"};

    cout<<"length of the string: " << s.size() << endl;

    vector<string>&& out = subStringKDistinct(s, 4);

    

    for (auto& e : out){

        

        cout<< e << endl;

    }

    

    gettimeofday(&tv,NULL);

    long te = tv.tv_sec * 1000 + tv.tv_usec / 1000;

    

    cout<< "running tmie is : " << te - ts << endl;

    return 0;

}