PositionsAverage.java

/*
Suppose you have 4 numbers: '0', '9', '6', '4' and 3 strings composed with them:

s1 = "6900690040"
s2 = "4690606946"
s3 = "9990494604"
Compare s1 and s2 to see how many positions they have in common: 0 at index 3, 6 at index 4, 4 at index 8 ie 3 common positions out of ten.

Compare s1 and s3 to see how many positions they have in common: 9 at index 1, 0 at index 3, 9 at index 5 ie 3 common positions out of ten.

Compare s2 and s3. We find 2 common positions out of ten.

So for the 3 strings we have 8 common positions out of 30 ie 0.2666... or 26.666...%

Given n substrings (n >= 2) in a string s our function pos_average will calculate the average percentage of positions that are the same between the (n * (n-1)) / 2 sets of substrings taken amongst the given n substrings. It can happen that some substrings are duplicate but since their ranks are not the same in s they are considered as different substrings.

The function returns the percentage formatted as a float with 10 decimals but the result is tested at 1e.-9 (see function assertFuzzy in the tests).

Example:
Given string s = "444996, 699990, 666690, 096904, 600644, 640646, 606469, 409694, 666094, 606490" composing a set of n = 10 substrings (hence 45 combinations), pos_average returns 29.2592592593.

In a set the n substrings will have the same length ( > 0 ).

Notes
You can see other examples in the "Sample tests".
*/

public class PositionsAverage {
    public static int compareThem(String one, String two){
        int count=0;
        for(int i=0;i<one.length();i++){
            if(one.charAt(i) == two.charAt(i))count++;
        }
        return count;
    }
    public static double posAverage(String s) {
        // your code
        int diff = 0;
        s=s.replaceAll(", "," ");
        String[] arr = s.split(" ");
        double ans = 0.0;
        int comb = 0;
        for(int i=0;i<arr.length;i++)
        {
          String one = arr[i];
          for(int j=i+1;j<arr.length;j++)
          {
            String two = arr[j];
            diff = diff+compareThem(one,two);
            comb = comb+arr[j].length();
          }
        }
        ans = (double) (diff *100)/comb;
        return ans;
    }

    public static void main(String[] args) {
        System.out.println(posAverage("466960, 069060, 494940, 060069, 060090, 640009, 496464, 606900, 004000, 944096"));
    }
}