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  1. Prepare
  2. Algorithms
  3. Strings
  4. Two Characters
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Two Characters

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  • luiz_janela
     + 0 comments

    Just realized that i invested like 1 hour doing a algorythm that recursively check every possibility with any numbers of char set above 2. Almost passed every test, but the was a timeout issue. Folks out there pay attention to the last sentence... TWO CHARACTERS, not 3, not 4, not N, just maximum of two:

    Given a string, remove characters until the string is made up of any two alternating characters. When you choose a character to remove, all instances of that character must be removed. Determine the longest string possible that contains just two alternating letters.

  • anarod_val25
     + 0 comments

    Hint, there is no need to be efficient here, so just try what seems eassiest:

    int alternating(const string& str, char a, char b) {
    char prev = 0;
    int len = 0;
    for (char c : str) {
        if (c != a && c != b) continue; 
        if (c == prev) return -1;       
        prev = c;
        len++;
    }
    return len;
}

int alternate(string s) {
    set<char> str_set(s.begin(), s.end());
    vector<char> uniques;
    
    copy(str_set.begin(), str_set.end(), std::back_inserter(uniques));
    int bgs = 0;
    
    for(int i = 0; i<uniques.size(); i++){
        for (int j = i+1; j<uniques.size(); j++) {
            int len = alternating(s, uniques[i], uniques[j]);
            if(len>0 && len>bgs){
                bgs = len;
            }
        } 
    }
    
    return bgs;
}

  • afzal_saiyed931
     + 0 comments
    def alternate(s):
    # Write your code here
    max_length = 0
    uniques = set(s)
    for a, b in combinations(uniques, 2):
        filtered = [i for i in s if i == a or i == b]
        l = len(filtered)
        valid = True
        for i in range(1, l):
            if filtered[i] == filtered[i-1]:
                valid = False
                break
                
        if l > max_length and valid:
            max_length = l
            
    return max_length

  • ilovemylittlecr1
     + 0 comments

    Fastest Solution in C++

    include

    include

    using namespace std;

    int main(){ ios::sync_with_stdio(false); cin.tie(nullptr);

    int n;
cin >> n;
cin.ignore();

string s;
cin >> s;

vector<int> freq(26); 

for(char c : s) ++freq[c - 'a'];

int max_len = 0;
for(char c1 = 'a'; c1 <= 'z'; ++c1) {
    if(freq[c1 - 'a'] == 0) continue;

    for(char c2 = c1 + 1; c2 <= 'z'; ++c2) {
        if(freq[c2 - 'a'] == 0) continue;
        if(abs(freq[c1 - 'a'] - freq[c2 - 'a']) > 1) continue;
        if(freq[c1 - 'a'] + freq[c2 - 'a'] < max_len) continue;

        char last = '\0'; int len = 0;

        for(char c : s) {
            if(c == last) { len = 0; break; }
            if(c != c1 && c != c2) continue;
            last = c; ++len;
        }

        max_len = max(max_len, len);
    }
}

cout << max_len << endl;

return 0;

    }

  • h2017339
     + 0 comments

    return 0 and be surprised