Sorting string array as per numeric value

Question

I have a string array. This array is made of three integer array. But each of the Integer is followed by a character. Either l or p or r. now my aim is to sort the string array according to int values. Array sort or Collection.sort does not work properly. In my case if the array is {-2l 1r 0p 4p 3l} the answer should be {-2l 0p 1r 3l 4p}.

  String[] left = new String[starts.length];
            String[] right = new String[ends.length];
            String[] points_fast = new String[points.length];

            for (int i = 0; i < starts.length; i++) {
                left[i] = (starts[i] + "l" + " ");
            }
            for (int i = 0; i < ends.length; i++) {
                right[i] = (ends[i] + "r" + " ");
            }
            for (int i = 0; i < points.length; i++) {
                points_fast[i] = (points[i] + "p" + " ");
            }
            String[] add = new String[left.length + right.length + points_fast.length];
            // add=l+r+p;
            System.arraycopy(left, 0, add, 0, left.length);
            System.arraycopy(right, 0, add, left.length, right.length);
            System.arraycopy(points_fast, 0, add, left.length + right.length, points_fast.length);

my aim is to sort the array "add". N.B I tried to convert it to list and then use collections.sort. It does not work.

You mean hash map??

Tasmin
– Tasmin

2016-06-21 22:47:39 +00:00
Commented Jun 21, 2016 at 22:47 — Tasmin
– Tasmin, Commented Jun 21, 2016 at 22:47

Community · Accepted Answer · 2020-06-20 09:12:55Z

2

I hope this satisfy your solution: you just need to use the Collection.sort and override the comparator

 List<String> mnames1 = Arrays.asList("-2l", "1r", "0p", "4p", "3l");
    System.out.println(mnames1+" before");
    Collections.sort(mnames1, new Comparator<String>() {
        @Override
        public int compare(String a, String b) {
            String m = a.substring(0,a.length()-1);
            String n = b.substring(0,b.length()-1);
            return Integer.compare(Integer.parseInt(m),Integer.parseInt(n));
        }
    });
    System.out.println(mnames1+ "after");

output:

[-2l, 1r, 0p, 4p, 3l] before

[-2l, 0p, 1r, 3l, 4p]after

edited Jun 20, 2020 at 9:12

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answered Jun 21, 2016 at 22:44

Seek Addo

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9 Comments

Tasmin Over a year ago

No. I tried this too. Actually I found this help on some thread. But it does not work.

Seek Addo Over a year ago

@Tasmin what wasn't working. just try it and let me know the error message

Tasmin Over a year ago

My input was 1,1,3. So the array was like {1l.1r.3p} The error is Exception in thread "main" java.lang.NumberFormatException: For input string: "1r"

Seek Addo Over a year ago

@Tasmin are you making arrays with the dot or what{1.l 1r.3p} this is typo error right. when you use Arrays.asList(1l, 1r, 3p}; , this should work for you because is the same i tried with.

Tasmin Over a year ago

no. in the array there is no dot between the int values and the alphabet l/p/r.

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