How to sort characters in a string diagonally

Question

im splitting a string by the square number of his length..

String alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
int a = alphabet.length();
int b = (int)Math.round(Math.sqrt(a));

System.out.println(java.util.Arrays.toString(splitter(key, b))); 
// prints: [ABCDE, FGHIJ, KLMNO, PQRST, UVWXY, Z]

The splitter function:

public static String[] splitter(String s, int len) {
return s.split(String.format("(?<=\\G.{%1$d})", len));
}

What i want now is to sort it diagonal like this:

[0] = {A,B,D,G,K}
[1] = {C,E,H,L,P}
[2] = {F,I,M,Q,U}
[3] = {J,N,R,V,Y}
[4] = {O,S,W,Z,0}
[5] = {T,X,0,0,0}

I was trying to solve it with some loops by checking always if (i-1) >= i... but i get confused and kinda lost in here..

May I say that if you just had a 5x5 matrix this would be much easier? — Tim Biegeleisen, Aug 15 '17 at 05:43

Robby Cornelissen · Accepted Answer · 2017-08-15T06:47:51.293

The solution I created below

calculates the dimensions of the result matrix;
uses those dimensions to initialize a two-dimensional result array with NUL character values;
sets the values in the array based on the idea that for all elements on the same diagonal, the sum of their coordinates is constant.

String alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
double root = Math.sqrt(alphabet.length());
int width = (int) Math.round(root);
int height = width < root ? width + 1 : width;
char[][] result = IntStream.range(0, height)
                           .mapToObj(i -> new char[width])
                           .toArray(i -> new char[height][]);

int x = 0, y = 0, sum = 0;

for (char c : alphabet.toCharArray()) {
    result[x][y] = c;

    y = x == Math.min(sum, height - 1) ? Math.min(++sum, width - 1) : y - 1;
    x = sum - y;
}

System.out.println(Arrays.deepToString(result));

This yields the following output:

[[A, B, D, G, K], [C, E, H, L, P], [F, I, M, Q, U], [J, N, R, V, Y], [O, S, W, Z,  ], [T, X,  ,  ,  ]]

This was a really nasty problem, and I couldn't solve it (though I got it working for a square 5x5 matrix) +1 — Tim Biegeleisen, Aug 15 '17 at 06:10
@TimBiegeleisen Thanks! Cleaned it up a little more. It's almost readable now :) — Robby Cornelissen, Aug 15 '17 at 06:34

score 0 · Answer 2 · answered Aug 15 '17 at 01:55

0

Don't split and then try to sort in the matrix. Sort the array, cross the matrix in the diagonal pattern, place the sorted items in the matrix, merge the strings.

Now all you have to do is to find a way to iterate over the matrix diagonally.

answered Aug 15 '17 at 01:55

Paul92

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How to sort characters in a string diagonally

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