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Sort an Array of Version Numbers
  • Difficulty Level : Medium
  • Last Updated : 12 Aug, 2020

Given an array of strings arr[], consisting of N strings each representing dot separated numbers in the form of software versions.

Input: arr[] = {“1.1.2”, “0.9.1”, “1.1.0”}
Output: “0.9.1” “1.1.0” “1.1.2”

Input: arr[] = {“1.2”, “0.8.1”, “1.0”}
Output: “0.8.1” “1.0” “1.2”

Approach: Follow the steps below to solve the problem:

  • Create a function to compare two strings.
  • Store strings into a vector.
  • In order to compare two dot separated strings S1 and S2, iterate up to the length min(S1, S2) + 1 and compare each numerical parts of the string and sort accordingly.
  • Repeat the above steps for each pair of string and sort the array accordingly.

    Below is the implementation of above idea:

    C++




    // C++ Program to implement
    // the above approach
    #include <bits/stdc++.h>
    using namespace std;
      
    // Compares two strings
    int check(const string& a, const string& b)
    {
      
        int al = a.length();
        int bl = b.length();
      
        int i = 0, j = 0;
        while (i < al && j < bl) {
            if (a[i] == b[j]) {
                ++i;
                ++j;
            }
            else if (a[i] > b[j]) {
                return 1;
            }
            else
                return -1;
        }
      
        if (i == al && j == bl)
            return 0;
        if (i == al)
            return -1;
        return 1;
    }
      
    // Function to split strings based on dots
    vector<string> getTokens(const string& a)
    {
        vector<string> v;
        string s;
      
        // Stringstream is used here for
        // tokenising the string based
        // on "." delimiter which might
        // contain unequal number of "."[dots]
        stringstream ss(a);
        while (getline(ss, s, '.')) {
            v.push_back(s);
        }
        return v;
    }
      
    // Comparator to sort the array of strings
    bool comp(const string& a, const string& b)
    {
      
        // Stores the numerical substrings
        vector<string> va, vb;
        va = getTokens(a);
        vb = getTokens(b);
      
        // Iterate up to length of minimum
        // of the two strings
        for (int i = 0; i < min(va.size(), vb.size());
             i++) {
      
            // Compare each numerical substring
            // of the two strings
            int countCheck = check(va[i], vb[i]);
      
            if (countCheck == -1)
                return true;
      
            else if (countCheck == 1)
                return false;
        }
      
        if (va.size() < vb.size())
            return true;
      
        return false;
    }
      
    // Driver Code
    int main()
    {
      
        vector<string> s;
        s.push_back("1.1.0");
        s.push_back("1.2.1");
        s.push_back("0.9.1");
        s.push_back("1.3.4");
        s.push_back("1.1.2");
        s.push_back("1.1.2.2.3");
        s.push_back("9.3");
      
        // Sort the strings using comparator
        sort(s.begin(), s.end(), comp);
      
        // Display the sorted order
        for (int i = 0; i < s.size(); i++) {
            cout << s[i] << endl;
        }
        cout << endl;
        return 0;
    }
    Output:
    0.9.1
    1.1.0
    1.1.2
    1.1.2.2.3
    1.2.1
    1.3.4
    9.3
    

    Time Complexity: O(N*L*logN), where N is the total number of version strings, L is the maximum length among those strings.
    Auxilairy Space: O(N * L)

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